'Genesis' (Story Code 271) by Brannon Braga

Aboard the U.S.S. Enterprise the daily routine continues; while Doctor Crusher prepares a synthetic T-cell for a flu-ridden Lieutenant Barclay, Lieutenant Commander Data prepares for the birth of Spot's kittens, and Nurse Ogawa announces that she is pregnant. Lieutenant Worf tests the ship's weapon upgrades, but one of the torpedoes malfunctions and veers off course; a bored Captain Picard leaves in a shuttle with Data to retrieve the missile. But while they are away, the crew begins exhibiting strange behaviour: Worf becomes more aggressive, Counselor Troi complains of the cold, Barclay becomes hyperactive, and Commander Riker has difficulty concentrating. Worf, now almost primal, bursts into Troi's quarters and forces himself upon her while she lies in a hot bath; when she tries to stop him, he viciously bites her on the cheek. The two are taken to Sickbay, where Worf suddenly spits venom at Doctor Crusher and then escapes; Riker tries to alert Starfleet, but is unable to remember the code for the secure channel… Some time later, Picard and Data return to the Enterprise, only to find it adrift in space; the ship's computers are down and power systems are off-line, and bizarre animal noises can be heard throughout the vessel. The two officers investigate Troi's quarters and discover that she has transformed into a hideous, amphibian-like creature; Data determines that her DNA has been altered, causing her cells to mutate. Heading for the Bridge, they find Riker, now a Neanderthal - somehow, something is causing the entire crew to de-evolve...

Patrick Stewart (Captain Jean-Luc Picard), Jonathan Frakes (Commander William Thomas Riker), LeVar Burton (Chief Engineer Lieutenant Commander Geordi La Forge), Michael Dorn (Security Chief Lieutenant Worf), Gates McFadden (Doctor Beverly Crusher), Marina Sirtis (Councelor Deanna Troi), Brent Spiner (Lieutenant Commander Data), Patti Yasutake (Ogawa), Dwight Schultz (Lieutenant Reginald ‘Reg’ Barclay), Carlos Ferro (Ensign Dern), Majel Barrett (Computer Voice)

Directed by Gates McFadden
Produced by Ronald D. Moore and Peter Lauritson
Co-Produced by Brannon Braga
Executive Producers Jeri Taylor, Michael Piller and Rick Berman

TX:
21st March, 1994

Notes:
*Featuring Captain Jean-Luc Picard, Commander William Thomas Riker, Chief Engineer Lieutenant Geordi La Forge, Security Chief Lieutenant Worf, Doctor Beverly Crusher, Councelor Deanna Troi, Lieutenant Commander Data and Lieutenant Reginald Barclay