On stardate 4187.3, he participated in an operation secretly condoned by the Kzinti government, the objective of which was to regain control of a Slaver stasis box that had been found on Kzin and subsequently delivered into the custody of Starfleet. Having lured the USS Enterprise's shuttlecraft Copernicus to a small, icebound world in the Beta Lyrae system, Flyer and several fellow Kzinti ambushed the shuttle's crew using illegally-possessed phasers, in violation of the Treaty of Sirius. They took Commander Spock and Lieutenants Hikaru Sulu and Nyota Uhura prisoner aboard the Claw, and confiscated the box.
On Chuft-Captain's orders, Flyer opened the stasis box, among the contents of which was discovered a Slaver weapon, as the Kzinti had hoped. He then oversaw the moving of the Starfleet prisoners to the surface to be used as subjects in testing the weapon, securing them in a police web. Flyer advised Chuft-Captain as to the operation of the weapon and the uses of its varied functions as each was tested. When fellow crew member Telepath's pressure suit was damaged during the testing of one setting, Flyer aided "Fourth" in carrying him to safety aboard the Claw, and subsequently reported back to Chuft-Captain on his condition.
After another setting caused the deactivation of the police web, allowing Sulu and Spock to temporarily escape with the weapon, Flyer assisted Chuft-Captain, who had been wounded by Spock, back to the Claw. Once the weapon and prisoners had been reacquired by the Kzinti, Flyer participated in a conversation with the weapon's artificial intelligence, suggesting that it provide a description of star positions in its home sector in order to facilitate a determination of how long it had been in the stasis box. Subsequently, Flyer left the ship with Chuft-Captain, Telepath, and "Fourth" to test what they believed was the weapon's most powerful setting. However, having determined itself to have fallen into enemy hands, the weapon instead activated its self-destruct mechanism, killing Flyer and the other Kzinti and severely damaging their ship. (TAS: "The Slaver Weapon")