It is several years after the events of the first movie, and David Herdeg (the survivor of the Philadelphia Experiment from the first film) and Allison (the woman from 1984 he fell in love with) have married and have a child. David awakes, in agony, to a changed world. Germany won World War II and the United States is now about to mark 50 years as a Nazi conquest.

When a man awakens from a coma only to discover that someone has taken on his identity, he teams up with a young woman to prove who he is.

A biochemist and his dishy wife arrive in Berlin for a conference at which a scientist and his controversial Arab funder will announce breakthrough research. While his wife checks into the hotel, he grabs a cab to return to the airport for his briefcase, left at the curb. En route, an auto accident puts him in a coma, from which he awakes four days later without identification and with gaps in his memory. He goes to the hotel: his wife refuses to recognize him and another man has claimed his identity. With help from a nurse, the cab driver, a retired Stasi agent, and an academic friend, he tries to unravel what's going on. Is the answer in the briefcase?