Title: The Man Who Brings a Sun
Era: Post Dominion War
Setting: Starship
A Starfleet officer was buried in Starfleet Headquarters and nearly starved to death while awaiting rescue from beneath rubble so deep the transporters couldn't get to him. He recovered, though he needed a few replacement organs and a new arm, and even ended up ship-bound for the final attack of the Dominion War (he was a former Starship Captain who had been transfered to SF Command to teach and in administrative duties, and was returned to active starship captaincy due to the lack of said officers). He has a fairly small, but fast ship (pick one of the defense ships, like the Norway or something), and has suddenly gone missing.
Having hand-picked his crew, he selected many people who were hurt in the Breen attack on Earth, as well as others who lost ships or loved ones to the Chintoka attack. He has on board his ship a device capable of starting a low, but destructive, reaction in a small planetary body: basically, a device mannered after terraforming "star reignition" devices. And he's going to slam it into the single moon of the Breen homeworld: the equivalent of adding a burning moon to their sky. This would raise temps on Breen a lot, as well as ambient radiation, and ruin the place. A very good portion of his crew is in on this, and willing to die for this, and it would be a diplomatic nightmare, not to mention an atrocity.
The crew comes into this as one of the few ships in the immediate area, and the only one that manages to catch a stray signal. A lower-ranked officer on the ship that has gone rogue has done his best to send out a disguised signal. He's an ensign, a science officer, and terrified of getting caught, but he knows that what his Captain is doing is wrong, and he's trying to stop it. Irregular contact with the ensign will be the only "inside" help the crew have in stopping a captain bent on revenge...
The Doc
So you think, 'Might as well,
Dance a Tango to Hell,
at least I'll have Tangoed at all.'
-- "Rent," Jonathan Larson