Special Sub-Topic: Mysteries of the 24th Century Click Here To Play: Mysteries of the 24th Century

In the TNG episode "Conspiracy", who turned out to be the mastermind behind the plot to take over Starfleet?

Commander Remmick. The argument could be made that it was really the mother parasite inside Remmick who was behind the plot, but that wouldn't make a very good trivia question. ;)

Who killed the Cardassian collaborator Vaatrick?

Major Kira. As a member of the Bajoran underground, Major Kira killed Vaatrick after he discovered her trying to steal his list of Cardassian collaborators.

Who sent the subliminal message to Tuvok that caused him to attack several of the Voyager crewmembers?

Teero. Teero's mind control almost caused the Maquis crewmen to deposit the Federation officers on an M-class planet in the Delta Quadrant, after taking over Voyager.

Who was the cellularly altered assassin who tried to kill Chorgan in the TNG episode "The Vengeance Factor"?

Yuta. Commander Riker had to overcome his attraction to Yuta by shooting her three times. Yuta was looking for revenge on the Lornack clan for the massacre of her own family, the Tralesta clan.

Who was responsible for giving the Cardassians the location of the Kendra Valley resistance fighters?

Kai Opaka. Kai Opaka sacrificed her own son and 42 other freedom fighters in order to prevent the Cardassians from wiping out every village in the area.

Who steals The Doctor and brings him to a hospital ship?

Gar. The Dralian trader Gar stole The Doctor's mobile emitter while he was being treated aboard Voyager. This episode, "Critical Care", forced The Doctor to confront some serious ethical issues.

The Enterprise crew solved the mystery of the U.S.S. Brattain by the release of what element?

Hydrogen. Hydrogen, otherwise known as "one moon circling," was identified by Counselor Troi, who was largely responsible for rescuing the Enterprise in this episode, "Night Terrors".

Who kills Jadzia Dax in the DS9 episode "Tears of the Prophets"?

Gul Dukat. Gul Dukat was possessed by a Pah-wraith when he mortally wounds Dax and destroys the sacred orb, causing the wormhole to implode.

In the episode "Tinker, Tenor, Doctor, Spy", who is the alien who spies on The Doctor's daydreams?

Phlox. The Doctor daydreams about being the "Emergency Command Hologram" and firing the imaginary "photonic cannon" at a Borg sphere.

Who was responsible for the series of memory rapes aboard the Enterprise?

Jev. Jev attacked Counselor Troi, Commander Riker, and Doctor Crusher, and then made it appear that his father had actually been responsible for his crimes.

Who murders several members of the Shakaar Resistance Cell in the DS9 episode "The Darkness and the Light"?

Silaran. After putting herself and the O'Briens' unborn baby in serious danger, Kira manages to kill Silaran.

What happens to make the Voyager crewmembers realize that they are being held captive by the Dream Aliens?

The warp core explodes, but doesn't hurt Captain Janeway. Chakotay's use of a technique called 'lucid dreaming' is part of what saves the Voyager crew from the Dream Aliens in this episode, "Waking Moments".

Who was responsible for the death of the Ferengi scientist Dr. Reyga?

Jo'Bril. Jo'Bril was trying to steal Dr. Reyga's technology for the metaphasic shield.

What missing Klingon artifact do Worf, Dax, and Kor search for in the Gamma Quadrant?

The Sword of Kahless. After finding the sword, Worf and Kor discover that it somehow turns Klingons against each other, so they transport it into space.

Neelix discovers that the traitor aboard Voyager is whom?

Jonas. Jonas was giving Seska and the Kazon information about Voyager. Although Neelix first suspected Tom Paris, he eventually discovered the truth about Jonas.

Who was responsible for the deaths in the plasma stream of the Enterprise's nacelle?

Lt. Pierce. Lt. Pierce left behind a telepathic echo in the nacelle, after discovering his girlfriend cheating on him during the construction of the Enterprise at the Utopia Planetia shipyard.

Chief O'Brien is sent to infiltrate what Alpha Quadrant crime ring?

Orion Syndicate. Chief O'Brien's experience as a spy was bittersweet. Although his mission was successful, he felt partly responsible for sending his friend Bilby to his death.

Who was responsible for the death of the Banean physicist Tolen Ren in the Voyager episode "Ex Post Facto"?

the Banean doctor. Tuvok was able to prove Tom's innocence after mind-melding with him.

Who was responsible for the death of the scientist Dr. Apgar?

Dr. Apgar himself. Dr. Apgar was trying to disrupt Commander Riker's beam-out because he was afraid that the Enterprise would discover that he was trying to sell his new technology as a weapon.

Who did Ezri Dax discover was killing people aboard Deep Space Nine with a TR-116 rifle?

Chu'lak. In "Field of Fire", Ezri uses the expertise of Joran, one of Dax's former incarnations, to help her solve the murders aboard DS9.