|Sebastian Stan as Bucky Barnes - Marvel Studios|
If you need to be brought up to speed on the Winter Soldier story - in the comic books, Bucky was found in a frozen state of suspended animation by the Soviets and trained to be a master assassin, just like the Black Widow. He has no memory of his past life, so the Soviets send him on a mission to kill Captain America. There's no word from Marvel about how closely they will follow the story in the books, but it's a safe bet that major portions of it will be used in the movie.
I like how the fan used dialogue from the comic books in this clip. The script is from a scene in which Natasha Romanoff (Black Widow) and S.H.I.E.L.D. Director, Nick Fury, tell Steve Rogers (Captain America) what they know about the Winter Soldier.
Fury: They called him "Winter Soldier". Supposed to be the KGB's secret weapon. Story went that they found him on ice and only woke him up for the big gigs.
Natasha: He's very real. He was one of my trainers back in the red rooms.
Steve: You can't seriously be implying that Winter Soldier person is Bucky?
Natasha: We were hoping you could tell us. You saw him last night.