(written from a Production point of view)
The Enterprise discovers a colony full of rapidly-aging scientists. Whatever caused the rapid aging afflicts the ship´s landing party as well. Kirk, Spock, McCoy, and Scott are shocked to discover they are aging decades each day and will soon die unless a cure can be found. The unaffected Chekov may be their only hope for survival.
The USS Enterprise is on a routine mission to resupply the experimental colony at Gamma Hydra IV. Kirk, Spock, McCoy, Scott, Lt. Galway, and Ensign Chekov beam down. While the landing party is spread out looking for the missing colonists, Chekov wanders into a darkened building where he had been bidden search. As the lights come on, they reveal the dead body of a very old man – and Chekov runs out, terror-stricken. Chekov is panicking and is in the full throes of terror. The rest of the landing party goes in to investigate. McCoy reveals the cause of death to be natural causes, extreme old age. Spock finds this impossible, since he had checked the records prior to the group beaming down and found that none of the colony members were over thirty. Then two elderly people wander in – these are Robert Johnson, who claims to be only twenty-nine; and his wife, Elaine who claims to be twenty-seven.
- "Captain's log, stardate 3478.2. On a routine mission to resupply the experimental colony at Gamma Hydra IV, we discovered a most unusual phenomenon. Of the six members of the colony, none of whom were over thirty, we found four had died and two were dying... of old age."
In the Enterprise in sickbay, Kirk tries to question Robert Johnson, but being of advanced age, he doesn't quite understand what the captain is asking him. He fills in his passengers, Commodore Stocker, Yeoman Doris Atkins, and Dr. Janet Wallace, Wallace also being an old flame of Kirk's past. Kirk promises to keep them all informed and that they will remain in orbit until the mystery is solved. Commodore Stocker expresses his pressing concern to reach Starbase 10, and Kirk says he will do everything he can to get Stocker there. Everyone leaves the briefing room and Dr. Wallace and Kirk reminisce about the past for a moment and how their careers got in the way of their relationship over six years ago.
Kirk goes to the bridge and gives Sulu the order to maintain orbit, and Spock informs him that a rogue comet passed near the planet some time ago, but is unsure if it had any effects on the planet. Commodore Stocker tries to again push the Enterprise to leave immediately for Starbase 10, claiming the instruments there would be more effective. Kirk politely refuses the Commodore's request and leaves the bridge giving the command again to maintain orbit, much to Sulu's and Spock's puzzlement.
Meanwhile, a perplexed Lieutenant Galway visits McCoy complaining about suffering a sudden loss of hearing. Kirk, in his quarters, calls Spock on the bridge and informs him to look into a comet that had recently passed the planet. Spock, of course, replies he is already doing so as per Kirk's orders, leaving Kirk a little confused. He then goes to sickbay complaining of shoulder pain, and jokes about McCoy's hair getting a little grayer. McCoy's initial exam reveals advanced arthritis in Kirk's shoulder, which Kirk doesn't believe at first. But then Scott walks in, complete with gray hair and wrinkles.
- "Captain's log, stardate 3479.4. The Enterprise personnel who beamed down to the planet's surface – Dr. McCoy, Engineer Scott, Mr. Spock, Lieutenant Galway, and myself – are all showing definite signs of aging. Only Ensign Chekov appears to be normal."
Everyone that had been in the landing party is showing definite signs of accelerated aging, with the sole exception of Chekov. Most of the party members are aging at approximately thirty years a day (Galway, despite being the youngest of those afflicted, appears to be aging at a vastly faster rate than anyone else), and McCoy is at a loss for the cause. He has run a complete physical on Chekov and found nothing to explain it. Spock estimates that they all have less than a week to live and that in lesser time, they will be little more than mental vegetables. Though Spock is showing no obvious physical signs, he admits to suffering from lethargy, memory and vision loss, and the ship's temperature is feeling increasingly colder to him. Kirk sends Scott and Galway back to their duties and leaves McCoy to do yet another physical on Chekov.
As Kirk heads back to the bridge, he exchanges a mildly flirtatious conversation with the concerned Dr. Wallace. The tone changes however, when Kirk realizes that her deceased husband, Theodore Wallace, was 26 years her senior. Kirk rejects her advances, and inquires if Dr. Wallace's affections to him are because of his current appearance, and also concerned it's out of pity for his sad condition.
Sitting at his navigation console on the bridge, Chekov gripes to Sulu about McCoy's constant examinations of him and him giving all sorts of samples. "If I live long enough, I'm going to run out of samples." An elderly Kirk arrives at the bridge while a concerned Commodore Stocker looks on, and the bridge crew can see that Kirk's advanced age is clearly taking its toll. Kirk gives orders, then forgets giving them. He even falls asleep in his command chair. A gray-haired Spock wakes him and informs him that the comet is indeed the source of the problem. By now, even Spock appears to be tired. The orbit of Gamma Hydra IV took the planet through the comet's tail. Though no regular levels of radiation were detected, there were extremely low levels of radiation, which is the probable cause. Kirk then orders Lieutenant Uhura to send a coded message to Starfleet and to use code 2 since they are close to the Romulan Neutral Zone. Uhura reminds Kirk that the Romulans have already broken code 2. A befuddled Kirk orders her to use code 3 and to relay the information about the comet. He then tells Sulu to move the ship to a higher orbit, and when Sulu indicates that he had already given that command, he yells, "I fail to understand why my orders are repeatedly being questioned!"
McCoy confirms the radiation theory, and Kirk returns to the bridge. Spock then informs McCoy that the ship has become increasingly cold and he's had to increase the temperature in his own quarters to 125 degrees, to which McCoy informs him that he will not be making house calls to Spock. Dr. Wallace then tells McCoy that none of the conventional means for radiation therapy will work in this case.
In a corridor, Commodore Stocker meets with Spock, informing him of his concern for Kirk's ability to command. He asks Spock to take over as captain, since Vulcans have a much longer life span than Humans. Spock reminds the commodore that he is also feeling the effects of the aging and that he also is half Human. Stocker asks Spock to conduct a competency hearing, which according to regulations is Spock's duty as first officer. Spock, wanting to spare Kirk of any more suffering than he's already going through and the humiliation of an almost guaranteed judgment against him, tells the commodore that he has duties to attend to. Stocker holds firm and insists to Spock that a competency hearing is mandatory by regulations. Spock reluctantly agrees and announces that he will convene the hearing at 1400 hours.
As McCoy continues to examine Chekov, an even more aged Lt. Galway arrives at sickbay and falls dead in Kirk's arms. McCoy speculates that Galway's metabolism caused the disease to affect her far more severely, resulting in her early death, and that they themselves don't have much more time. They may have days, perhaps hours left.
Spock conducts the competency hearing. Scott is by now much older, looking tired and depressed. Kirk and McCoy are also in terrible condition. A reluctant Atkins, Uhura, and Sulu testify about Kirk's failing abilities. McCoy also reluctantly confirms the computer analysis of his medical examination. Testifying, Kirk tries to maintain his control, but it is quite obvious that his mind and deteriorated body are failing, and he digs himself a deeper hole by going on a long, rambling speech in which he erroneously refers to the planet that they are orbiting as "Gamma Hydra II". He is removed from command and to his dismay, the inexperienced Commodore Stocker assumes command.
Kirk, despite his senility, has enough common sense to predict that Stocker, with no command experience, and in Kirk's words, a "paper pusher", would be a poor choice to command the Enterprise, and tries to order Spock to take command. When Spock rebuffs Kirk and reminds him that he no longer has power on the Enterprise, it deeply hurts him and temporarily causes a rift between the two. Kirk then fruitlessly tries to justify his command ability to Janet, telling her that his brain is still as sharp as it ever was, despite evidence to the contrary. Kirk asks Wallace if she sees him getting older for which she cannot provide an answer.
Later, a very old and gray Kirk and an equally-gray Spock and McCoy review again their beaming down to the planet. Spock then reminds them that the only time Chekov was not with them was when he went into the building, discovered the body, and ran out from the building scared half to death. McCoy postulates that the increased adrenaline levels somehow may have protected Chekov from being afflicted.
Stocker, who has no field experience, plots a shortcut to Starbase 10 through the Romulan Neutral Zone and, of course, the Romulans immediately attack. The Enterprise is quickly surrounded by several Bird-of-Prey ships, as a shocked and frozen commodore tries to decide what to do.
The Romulans continue to attack the Enterprise while Stocker tries to establish communication. Spock races against time and makes a crude serum, but it could either cure or kill. Kirk, unable to endure any longer and determined to get back to the bridge, demands the first shot stating he's about to die anyway (either from the serum, destruction of the ship or the aging process) – and upon receiving it, he starts to scream and writhe while held down with restraints on his bio-bed.
Stocker feels that the only way to get the Romulans to stop is by surrendering. But Chekov reminds him that Romulans do not take prisoners.
Suddenly, a fully-recovered Kirk arrives on the bridge and retakes command. On purpose, he instructs Uhura to post a message to Starfleet, using code 2, that he plans to self-destruct the ship and take all the Romulan ships with him by using the "recently installed" corbomite device. Spock looks exhausted, but relieved.
As expected, the Romulans tap into the message and start to move out of the way. Kirk uses this opportunity to warp the Enterprise out of the Neutral Zone and back to safety. McCoy is shown to be recovered, and informs Kirk that Scott is fine, though he pulled a muscle when his body reacted to the serum. The cure is a success, even if the procedure is very painful to humans, and even more for Vulcans. McCoy informs Spock that a super dose is already ready for him, and all breakable objects were removed from the infirmary, and they can start whenever Spock is ready. Spock is in bad shape, and he asks to receive it now. Kirk remarks that the events of the past day will be an experience they will remember, even in old age – which hopefully will still be far off. Kirk orders Sulu to take command of the Enterprise, steady as she goes, which the helmsman repeats. Kirk replies that he thought he already said that.
"Why, Bones, I believe you're getting gray!"
"Well, you take over MY job and see what happens to YOU!"
- - Kirk and McCoy, as Kirk notices McCoy's advanced aging
"I don't know what's causing it. A virus, a bacteria, or evil spirits, but I'm trying to find out."
- - McCoy to Kirk, on the aging effects
"What a stupid place to hang a mirror!"
- - Galway, as she sees her aged reflection in sickbay
"The heart is not a logical organ."
- - Wallace to Kirk, on her feelings for him
"Blood sample, Chekov! Marrow sample, Chekov! Skin sample, Chekov! If – if I live long enough, I'm going to run out of samples!"
"Oh, yes. I'll live. But I won't enjoy it."
- - Chekov and Sulu, as Chekov complains about his medical tests
"I'm not a magician, Spock, just an old country doctor."
- - McCoy, as Spock complains about his sensitivity to colder temperatures
"Now this isn't going to hurt a bit."
"That's what you said the last time."
"Did it hurt?"
- - McCoy and Chekov, as McCoy prepares another medical test on Chekov
"The man's a chair-bound paper-pusher."
- - Kirk to Spock, describing Stocker
"And you don't run a starship with your arms. You run it with your head."
- - Kirk, as he tells Wallace why he is still fit to command the Enterprise
"You traitorous... disloyal... you stabbed me in the back the first chance you get! Spock...! Get out... I never want to have to look at you again."
- - Kirk, blaming Spock for losing command
"I admit, I'm getting a little gray but radiation will do that to you."
- - Kirk
"Lieutenant Uhura, let me know if we contact any Romulan..."
(The ship is shaken by an impact.)
"I think we just made contact, sir."
- - Commodore Stocker and Uhura, as the Enterprise is being attacked by Romulans
- Bantam Books published a series of novelizations called "foto-novels," which took photographic stills from actual episodes and arranged word balloons and text over them, to create a comic book formatted story. The eleventh installment was an adaptation of this episode.
- Dr. Wallace's costume was made from drapes.
- Oversized uniform shirts were specially constructed for this episode so the characters would appear to be shrinking as they "aged."
- In this episode, Kirk makes a reference to the fictional "corbomite" device, which he first described in "The Corbomite Maneuver". Although Chekov was not on the bridge on that occasion, he obviously heard the story from someone, as he and Sulu exchange knowing looks when Kirk mentions the word.
- Shatner's hairline is inconsistent in this episode. As the aging effect first hits him, the hairline is receding, but for some reason, as he gets much older, his hairline advances again.
- No special effects shots were filmed for this episode. The entire Romulan attack is created by using stock footage from "Balance of Terror" and "Errand of Mercy". In addition, no actual Romulans appeared in this episode. They would not be seen again until "The Enterprise Incident".
- The brownish planet seen in this episode (a slightly color corrected version of the one used in "The City on the Edge of Forever"), reappeared in later episodes, as Gamma II in "The Gamesters of Triskelion", Arret in "Return to Tomorrow", Zeon in "Patterns of Force", Minara II in "The Empath", Platonius in "Plato's Stepchildren", Cheron in "Let That Be Your Last Battlefield", and Gideon in "The Mark of Gideon".
- Areel Shaw's line from "Court Martial" about how long it has been since she's seen Kirk is recycled by Janet Wallace in this segment.
- The script called for the aged Kirk to run from sickbay to the bridge, and gradually grow younger until he arrived. But as director Joseph Pevney told Allan Asherman in The Star Trek Interview Book, the slow speech patterns and actions of the aging Enterprise personnel were making the episode run long. So Kirk's reverse aging scenes were cut. However the "aging scene from older to younger" would be used in TNG: "Too Short a Season" on Admiral Mark Jameson, and in TNG: "Man of the People" involving Troi and Ves Alkar. Ironically in the 1971 Mission Impossible episode "Encore", Shatner guest-starred as an elderly gangster who thinks he's a younger man in 1937, and who, at the end, changes from a young man to an old man again.
- When Spock questions Uhura during the competency hearing, he twice clearly refers to Uhura's having signed her initials (note the plural) on a document. Lt. Uhura was never given a first name during the entire run of the series, which at the time lead some to believe she may have only had the single name "Uhura". However, this episode established that, due to having more than one initial, she must also have had a name other than "Uhura".
- This episode was produced in early August 1967.
- Kirk's age – 34 years old – is established in this episode.
- The proximity of the Gamma Hydra sector to the Romulan Neutral Zone in this episode is repeated in the opening scene of Star Trek II: The Wrath of Khan, when the Enterprise supposedly violates the zone while patrolling near the sector. However, in the movie it's the Klingons who attack.
- In The World of Star Trek (3rd ed., p. 73), William Shatner relates that he endured an excruciating make-up session for this episode – all for nothing, because the shooting day was just about to end. The producers caught his exasperation in an infamous blooper, wherein he declares, "Bob Justman, I'm going home now... after spending three hours putting this [expletive deleted] make-up back on – and it's your fault!"
- According to Walter Koenig, director Joseph Pevney wanted to shoot a close-up of Chekov's eyes as he sees the aged dead body in surprise. However, Koenig blinked each time it was tried, and it took fifteen takes to do it right. However, it's not in the finished episode, probably deemed unsuitable. Koenig also felt that Chekov seemed younger in this episode than in any other, claiming that his reaction upon discovering the corpse in the teaser was more like the reaction of a 15-year-old than that of a Starfleet officer who had sat on the bridge of the Enterprise. 
- The end credits of this episode include a make-up test shot of William Blackburn as a Tellarite. He discusses his experience in an interview on the remastered second season DVD collection of the series issued by Paramount and CBS Home Video.
- The last shot of the episode is lifted from "Amok Time". Note the wig there on Walter Koenig, which he didn't have on for the entire episode.
- Dr. Janet Wallace's reason for being aboard the Enterprise is never revealed. She's just "there" in Act I, and her expertise as an endocrinologist later turns out to be fortuitous. It's possible, however, that she and Commodore Stocker have both been assigned, and are being conducted, to Starbase 10.
- This is the first time McCoy is aged using makeup in order to look much older than he is. The second time is in TNG: "Encounter at Farpoint". It is interesting to note how similar both aged McCoys look.
- McCoy's Southern dialect also grows noticeably thicker as he ages.
- One memorable outtake features Beverly Washburn getting stuck on a line, before blurting out, "I FEEL LIKE HELL!" 
- Story outline "Hold Back Tomorrow" by David P. Harmon: May 1967
- Revised story outline "The Deadly Years": 5 June 1967
- First draft teleplay: 19 June 1967
- Second draft teleplay: 3 July 1967
- Revised draft by Gene L. Coon: mid-July 1967
- Final draft teleplay by Coon: 27 July 1967
- Additional page revisions: 31 July 1967, 2 August 1967, 3 August 1967
- Filmed: 3 August 1967 - 11 August 1967
- Day 1 – 3 August 1967, Thursday – Desilu Stage 10: Ext. Gamma Hydra IV surface, Int. Colony building; Desilu Stage 9: Int. Sickbay
- Day 2 – 4 August 1967, Friday – Desilu Stage 9: Int. Bridge
- Day 3 – 7 August 1967, Monday – Desilu Stage 9: Int. Corridors, Sickbay
- Day 4 – 8 August 1967, Tuesday – Desilu Stage 9: Int. Sickbay, Bridge, Briefing room
- Day 5 – 9 August 1967, Wednesday – Desilu Stage 9: Int. Kirk's quarters, Briefing room
- Day 6 – 10 August 1967, Thursday – Desilu Stage 9: Int. Briefing room, Corridor, Sickbay
- Day 7 – 11 August 1967, Friday (Half Day) – Desilu Stage 9: Int. Sickbay
- Original airdate: 8 December 1967
- Rerun airdate: 16 August 1968
- First UK airdate: 29 June 1970
Video and DVD releasesEdit
- Original US Betamax release: 1986
- UK VHS release (two-episode tapes, CIC Video): Volume 21, catalog number VHR 2356, release date unknown
- US VHS release: 15 April 1994
- UK re-release (three-episode tapes, CIC Video): Volume 2.4, 7 April 1997
- Original US DVD release (single-disc): Volume 20, 13 February 2001
- As part of the TOS Season 2 DVD collection
Links and referencesEdit
- James Doohan as Scott
- George Takei as Sulu
- Nichelle Nichols as Uhura
- Majel Barrett as Christine Chapel and the computer voice
- Walter Koenig as Chekov
- Felix Locher as Mr. Johnson
- Carolyn Nelson as Yeoman Atkins
- Laura Wood as Mrs. Johnson
- Beverly Washburn as Arlene Galway
- Frank da Vinci as Brent
- Roger Holloway as Roger Lemli
- Eddie Paskey as Leslie
- Unknown actors as
2233; 2238; 2240; 2243; 2261; 2265; adrenal gland; adrenaline; aging; Aldebaran III; arthritis; astrophysics (astronomical section); Atomic Age; biochemistry; "Bones"; bone marrow; blood; blood type; bulletin; carbohydrate compound; class M; code 2; code 3; colony; comet; command order; commodore; corbomite; cosmic ray; dead zone; deaf; decency; diameter; emergency power; endocrinology; Fahrenheit; Federation; field command; flag officer (flag rank); fuel consumption report; Gamma Hydra; Gamma Hydra II; Gamma Hydra IV; guinea pig; hearing; heart; house call; hypersonic treatment; hyronalin; initials; junior officer; logic; magician; medical scanner; mile; morality; muscular strain; needle; nitrogen; oxygen; perigee; physical; plant; prosecuting attorney; pulled muscle; Quadrant 448; radiation; radiation poisoning; radiation sickness; radiation therapy; rank; ranking officer; red alert; reflex; Romulan; Romulan Bird-of-Prey; Romulan Empire; Romulan Neutral Zone; senility; senior officer; signature; skin; solar year; standard orbit; Starbase 10; Starfleet Command; Starfleet Regulations; stargram; vitamin; Vulcan; Wallace, Theodore; yeoman
- "The Deadly Years" at StarTrek.com, the official Star Trek website
- "The Deadly Years" at Memory Beta, the wiki for licensed Star Trek works
- "The Deadly Years" at Wikipedia
- "The Deadly Years" at MissionLogPodcast.com, a Roddenberry Star Trek podcast
| Previous episode produced:|
| Star Trek: The Original Series|
| Next episode produced:|
| Previous episode aired:|
| Next episode aired:|
| Previous remastered episode aired:|
|TOS Remastered|| Next remastered episode aired:|
"The Alternative Factor"