Warhead: Voyager finds a WMD with an onboard AI and beams it on board.
Paris is frantic because he forgot the anniversary of his first date with Torres, while Kim is happy because he gets to sit in the Captain's chair for the night shift.
Voyager diverts to investigate a distress call... Kim, HoloDoc and a random crewmember beam down to a planet and locate some sort of missile. Which starts talking to them.
They beam it aboard Voyager and the HoloDoc converses with it merrily. He breaks the news to it that it's not, as it believes, an organic being, but an artificial intelligence. Meanwhile, Janeway and Seven locate a crater where the AI's friend exploded - it's a WMD!
HoloDoc wants to salvage the AI from the weapon... however when they attempt to shut it down so they can transfer the AI to a holomatrix, it arms itself... Torres disables it with a pulse, but it has somehow transferred itself into the HoloDoc. It tells them it has to fulfill its mission and wants Voyager to take it there. Janeway has no choice but to comply, but sets about working out a way to outsmart the bomb. Why don't they just tell the computer to deactivate the HoloDoc? Oh, he's encoded the controls.
Neelix has a power node which uses the same technology as the weapon, and suggests the trader he got it from might know where it's from. Kim tries to reason with the bomb, to little effect.
Neelix's trader turns up, but he will only disarm the weapon on condition he gets to keep it for salvage. Janeway's not convinced that he won't sell it to someone who might use it though, so he pisses off back to his ship and tries to take the weapon by force. The weapon sends an antimatter burst through the transporter stream and blows the trader's ship up.
Meanwhile a whole pack of the weapons has detected Voyager and set off in pursuit.
Torres and Kim record a piece of the bomb's memory indicating its own people instructed it to crash. The war ended three years ago. The bomb isn't convinced though, and goes on a major paranoid rant. After Janeway's plan swings into action, Seven attempts to defuse the bomb, but gets zapped.
The bomb threatens to detonate, and Janeway calls its bluff. The other weapons turn up and announce they're taking the bomb to destroy its target... Kim attempts to reason with it some more, and it transmits the info to the other bombs, but they don't believe it.
Kim and Torres return the AI to the bomb, and it blows up the other weapons. Later, holodoc feels guilt over asking Kim to bring the bomb on board, and Kim is thanked by the helmswoman for not letting the ship get blown up. The end!