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Identity Crisis (episode)

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"Identity Crisis"
TNG, Episode 4x18
Production number: 40274-192
First aired: 25 March 1991
91st of 176 produced in TNG
91st of 176 released in TNG
  {{{nNthReleasedInSeries_Remastered}}}th of 176 released in TNG Remastered  
198th of 728 released in all
Geordi La Forge investigates vector analysis anomaly
Teleplay By
Brannon Braga

Story By
Timothy DeHaas

Directed By
Winrich Kolbe
44664.5 (2367)
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Template:Disambiguate La Forge and a former shipmate are the only officers left from an away mission five years ago – the others have transformed into aliens and disappeared.



In the observation lounge, Jean-Luc Picard, William Riker, Geordi La Forge, and Susanna Leijten are viewing a sensor log from an investigation Leijten and La Forge were part of five years ago, while attached to the USS Victory. They were investigating the disappearance of 49 colonists from the Tarchannen III outpost. The other members of the Victory away team, Brevelle, Mendez, and Hickman, have now deserted their posts without any warning. A Federation supply ship has spotted Hickman's stolen shuttle and it is heading back to Tarchannen III.

Act One

"Captain's log, stardate 44664.5. We've set a course to intercept Lieutenant Hickman's stolen shuttlecraft, and hopefully to discover the whereabouts of the other missing officers."

La Forge and Leijten go to Ten Forward to reminisce about their days on the Victory and catch up with events. When the Enterprise finds the shuttle, the helmsman reports that they have entered the Tarchannen system. Worf hails the shuttle but Hickman doesn't respond. The shuttle approaches the planet too fast and burns up in the atmosphere. However, sensors detect two more shuttlecraft on the surface, but no life signs. So Picard orders an away team to investigate.

On the surface, the away team discovers the shuttle that Mendez stole from the USS Aries. While La Forge checks out the shuttle, Leijten finds strange footprints in the sand, and she moves towards them for a closer look. Worf and Riker are having an uneasy time as if they are being watched, when he reported to Riker. La Forge returns with a chilling piece of evidence. Two torn Starfleet uniforms. La Forge notices that Leijten is missing. The other members of the team spread out to look for her. When La Forge follows some footsteps in the sand, he finds her staring blankly into the darkness. She claims she can feel the missing crew's presence. She starts to shake violently, screaming, as La Forge calls up a medical emergency beam-out.

Act Two

Leijten wakes up in a bed in sickbay. Dr Beverly Crusher reports that her blood chemistry is off and that she's had a histamine response to something unknown. Leijten feels compelled to return to the surface but Crusher orders her to stay on the Enterprise until she can find out what is wrong. Leijten protests, but Picard backs up Crusher's order.

Leijten and La Forge are walking in the corridor when Leijten's hands start to tremble. She states under fear that whatever is happening to the away team members is happening to her.

On the bridge, Data examines data collected from the survey. He has found some alien cells that don't belong to any known Tarchanen lifeform. While Data attempts to find a match for the cells and footprints, La Forge and Leijten decide to go through the mission log to see if there is any commonality they missed that would make the crew return to Tarchanen III to be abducted.

As they examine the logs, Leijten becomes agitated and demands to go back to the surface. As she leaves, she begins to shake uncontrollably and collapses. La Forge notices a strange blue growth pattern on the back of her neck and that her fingers have grown together.

Act Three

Leijten is in a dark room as she has developed an extreme sensitivity to light. The strange growth patterns now cover most of her body. La Forge comes to visit and comfort her. Crusher discovers that Leijten's cells have now changed to match the alien cells found on the surface. Crusher theorizes that the missing crew were not abducted, but transformed into a different species. Crusher informs La Forge that he will most likely be next and that he should stay in sickbay. He insists that he needs to work on the investigation.

He returns to engineering and begins to examine the logs again. He runs several scans on the data. Then he notices a slight shadow on the visual log that he cannot determine the source of. He tells the computer to create a holoprogram based on the sensor log data. As he goes to the holodeck he notices that his hand has begun to tremble as well.

Act Four

In the holodeck, La Forge uses the computer to remove people and their shadows from the simulation until only the strange shadow is left. He then uses vector analysis to determine the location of the object causing the shadow. He is shocked to discover a human sized invisible shape. As soon as he discovers it, he then slumps down in pain. He then finds the same physical changes that Leijten experienced are starting to happen in his body.

In sickbay, Crusher begins to understand what is happening and finds a parasite in Leijten's thymus. She discovers that her skin is starting to have a mimetic response to light and that the parasite is using her immune system to transform her body.

Dr. Crusher operates on Leijten and removes the parasite. She tries to find La Forge, but he has disappeared. The computer reveals the last location of La Forge and Picard sends Worf, Riker and a security detail to the holodeck. When they arrive they see what La Forge saw, and Worf discovers a grisly scene: La Forge's torn uniform and his VISOR. Riker steps back as he gazes at the eerie image, thinking that this is what the chief engineer has become. In the transporter room an invisible shape attacks the transporter operator and beams to the surface.

Act Five

Data develops a method to detect the invisible aliens using ultraviolet light from an emergency beacon. Crusher, the very quickly healed Leijten, Riker, Worf, and Data beam down to the surface. They find the nearly transformed La Forge, but Leijten is able to convince him to come to her.

On the starship, Crusher is able to save La Forge. Based on his own experience, he reports that the creatures are unintelligent: operating entirely on instinct. Captain Picard decides that Tarchanen III should be isolated. He orders warning beacons placed around the planet to warn others of the aliens there.

Memorable Quotes

"You're worried about Geordi aren't you?"
"I am an android; it is not possible for–"
(Crusher interrupts) "... you to feel anxiety."
"Starfleet personnel have vanished. Others may be at risk. We must do the best we can to find out why. However, I am... strongly motivated to solve this mystery."

- Dr. Crusher and Data - Listenfile info

Background Information

LeVar Burton makeup, Identity Crisis

LeVar Burton in full makeup

Story and script


Computer screen trek frame

The anomalous computer screen.

Mark and Brian interview

Mark Thompson and Brian Phelps interviewing Jonathan Frakes on set.

  • "Identity Crisis" was filmed between Wednesday 16 January 1991 and Friday 25 January 1991 on Paramount Stage 8, 9, and 16.
  • For a single frame (at approximately 17:08 on a Region 1 DVD and 16:27 on Region 2 DVD), a graphic displaying the Star Trek: The Next Generation logo can be seen on a computer readout in engineering.
  • Regarding the use of ultraviolet effects in the episode David Livingston recalled, "We were talking about how we're going to make these guys glow and Peter Lauritson says to me, 'Why don't we try ultraviolet?' I said because we had done a test the year before. I almost dismissed it, but then pulled out the tape and looked at it and said this stuff is great. [I] went to Michael Westmore and Bob Blackman and said we want to do this, and they designed these suits and we painted them with u/v and put these contact lenses into this woman's eyes that glowed. It was fabulous and we got Mark and Brian to walk around in these suits. LeVar looked fabulous.
"We used heavy blue light for the set lighting, and it's different lighting than you see elsewhere, because all of the source coming from behind the camera is blue light. That's a decision we made and it should look harsh, and unrealistic and not well lit because it's not lit from one single blue source. It's basically a beacon shining out. It looked different than anything else and that was intentional. What I was surprised at was how powerful the u/v reflected back, and MTV is using it a lot now. I liked our use because it was integrated into the story. We used it to make it work dramatically rather than doing it as an effect. To me, that was a major accomplishment. We didn't do it to just be glitzy, we did it because it tied in dramatically with the story." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 218)
  • It took four make-up artists six hours to apply the full Tarchannen III species make-up to LeVar Burton. According to Michael Westmore, it was the longest make-up ever done on The Next Generation. ("Departmental Briefing, Year Four: Make Up", TNG Season 4 DVD special feature)
  • First UK airdate: 19 October 1994


La Forge old visor

Older version of La Forge's VISOR

  • In the scenes set in the year 2362, crewmembers of the USS Victory are correctly seen wearing the old Season 1 and 2 Starfleet uniforms (La Forge wearing command red again) and using the early "dustbuster" type 2 phaser. La Forge additionally wears an older version of his VISOR.
  • Although the past scenes are set in 2362, the stardate given starts with "40", which would imply 2363.
  • The command of the USS Aries was previously offered to Riker upon the retirement of her captain, as seen in "The Icarus Factor".
  • When Crusher is ready to operate Leijten, one of the medical staff is seen to place a neural stimulator over her head, like the one prominently used on Riker in "Shades of Gray".
  • Other species that propagate by infusing other species with their DNA and transforming them include the Taresians, Kobali and Loque'eque.

Cast and characters


  • Michael Piller remarked, "It was a very complicated, complex production that the director did a terrific job on. It had scenes within scenes and I was very happy with the show. It may not have been one of the best scripts we wrote, but it's a great example of how those guys in production can really turn out a helluva product." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 218)
  • Winrich Kolbe recalled, "That was an interesting show and a lot of [work]. First of all, LeVar Burton is a hell of an actor and it's a lot of fun working with him, even though I'm sure there was a lot of pain and agony on his part going into that suit. Technically speaking we didn't make things any easier for him because we had to light everything with black light. So we're kind of restricted camerawise to do what we wanted to do because of all of those tremendous black light units. It was a hell of a set, but a technical nightmare. But everybody seems to be happy about it." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 218)
  • A mission report for this episode by Patrick Daniel O'Neill was published in The Official Star Trek: The Next Generation Magazine Vol. 16, pp. 54-56.


  • This episode was nominated for an Emmy Award for Outstanding Achievement in Makeup for a Series.

Video and DVD releases

Links and references


Also starring

Guest stars


Uncredited co-stars

Stunt double

Stand-ins and photo doubles


Aries, USS; bioscan; Bogrow, Paul; cc; cell wall integrity; chameleon; Cousteau; day watch; DNA; emergency beacon; emitter module; Federation; Federation supply ship; gene; EM scan; histamine; infrared sensor; interferometric frequency; ionizing radiation; ionosphere; kayolane; Malaya IV; medical tricorder; palm beacon; parasite; proximity detector; sandstorm; security lockout; sedative; sensor array; spectrographic analysis; Starbase 112; subspace; T-cell stimulator; Tarchannen; Tarchannen III; Tarchannen III species; Tarchannen system; thermosphere; time index; thymus; tricorder; turbolift; Type 7 shuttlecraft; Type 15 shuttlepod; ultraviolet radiation; vector analysis; Victory, USS; viral crèche; VISOR; visual recording device; warning beacons; Z-particle

External link

Previous episode:
"Night Terrors"
Star Trek: The Next Generation
Season 4
Next episode:
"The Nth Degree"

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