Setting:
Post-movie era (2298). The Crew serve on the USS Nobile, a Frontier-class scout vessel (17 crew total). The prime threat is the Tholian Assembly, which they have had a series of run-ins with.
Current plot Idea:
The USS Nobile come across a sleeper ship transporting a Vascian terrorist. 40 years ago, the terrorist, Alx Bien, was responisble for several attacks against the oppressive government before he suddenly vanished. Revived and learning that the war he fought has been over for more than 30 years, he decides it is time to go home and face the consequences of his actions.
The Vascian government disavows the terrorist and refuse to accept that he is the one he claims to be. It turns out Bien surrendered 40 years ago! His trial and confessions brought about a cease-fire wich eventually led to lasting peace among the Vascians. Bien is currently serving life in a maximum security prison.
Bien's return invalidates the very foundation of the peace settlement and may throw the Vascians back into war.
Behind the scenes:
There are a number of plots involved at this point. The most obvious plot is that the Vascians found Bien to have disappeared, arranged for a double. This double surrendered and confessed at what was essentially a mock-trial.
The Bien found by the Crew is actually a clone. He has most of the original Bien's memory and honestly believes he is him. He has only one goal - to attone for the crimes he believes he has commited.
And then there is Bien himself. Seeing his faction lose against its enemies, he allowed himself to disappear. He would allow the wounds of war to heal, for a time. Then his clone would reappear and start it all over again.