On 22 November 1963, Peter Miller, a young freelance reporter in Hamburg, West Germany, pulls his car over to listen to a radio report on the John F. Kennedy assassination in Dallas. As a result, he happens to be stopped at a traffic signal as an ambulance passes by on a highway.
He follows the ambulance and discovers it is en route to pick up the body of an elderly man who has committed suicide, leaving behind no family. Peter obtains the man's diary and learns the man was Salomon Tauber, a Jewish Holocaust survivor. Salomon Tauber's diary details information on his life in the Riga Ghetto during World War II, (including the name of the SS officer who ran the camp, Eduard Roschmann). Salomon's diary catalogues all of Roschmann's crimes, including the murder of a highly decorated Wehrmacht officer while attempting to flee at the end of the war.
Peter is filled with a determination to hunt Roschmann down, and he sets out to meet famed Nazi-hunter Simon Wiesenthal, who informs him about ODESSA, a secret organization for former members of the SS which is developing a missile guidance system for Nasserist Egypt. Wiesenthal explains that most of the Hamburg Police are members of ODESSA and not to be trusted. As Peter leaves, he is accosted by Israeli Mossad agents who suspect Peter of trying to harm Wiesenthal. Peter manages to convince the men that his true mission is to find and bring Roschmann to justice. The Israelis propose to send Peter deep undercover in the ODESSA. Peter agrees to the mission, and with the help of the Israelis, is provided with a cover identity. Peter is to be a former SS soldier who died recently in a nearby hospital. He does not inform his girlfriend Sigi, who was attacked in an attempt to get the whereabouts of Peter.
The Israelis drill Peter on all details of his cover identity in preparation of meeting with ODESSA. Complete with a new cover identity, Peter gains access to the inner ranks of the ODESSA. After getting through his first test, he is sent to get a fake passport from a forger who is working for ODESSA. While awaiting his train, Peter blunders by making a call to Sigi to assure her that he is OK. Thinking he is safe, he boards the train. Meanwhile, the ODESSA report back that Peter has made a call, and they work out that Peter is not who he says he is. An assassin is dispatched to kill him. Peter meets with the forger Klaus Wenzer, a shy, insecure young man living with his mother. Klaus tells Peter to return after the weekend to take passport photos but then calls him after midnight and tells him to return within the hour.
Suspicious, Peter rings Klaus' home from his hotel and, having had no answer, is wary and sees the armed assassin who is waiting for him. Peter sneaks into the house and awakes Klaus' mother: she mistakes him for a priest and begs him to pray for her son. He then tackles the assassin and manages to kill the man. Whilst exploring Klaus' safe, he uncovers a book, the ODESSA file, detailing every fake ID Klaus created and divulging the real identity of those he created the fake IDs for. Peter takes the file and hides it in a train station locker, later giving the key to Sigi, lest anything should happen to him.
Peter, victorious, returns to the Israelis and details all he has found but refuses to disclose the location of the file until Eduard Roschmann has been apprehended. The Israeli agents reluctantly agree to Peter's demands, and he then leaves for Roschmann's home, where he finds him living an opulent life as a munitions factory owner using an alias. Peter manages to gain access to the mansion and evade his security before confronting Roschmann at gunpoint. Peter reveals Salomon Tauber's diary to Roschmann, who attempts to deny everything, claiming Peter has been misled. Peter then discloses to Roschmann Salomon's description of the murder of a fellow German Wehrmacht officer at the end of the war. Peter goes through the unique details of the cowardly murder and then discloses that the Wehrmacht officer was in fact Peter's father. Roschmann, realising he is about to be exposed, panics and goes for his gun, forcing Peter to defend himself. Peter returns fire at Roschmann, killing the former SS officer who had killed his father.
The detailed ODESSA files obtained by Peter are used to arrest numerous Nazi war criminals, including high-ranking members of the police. Later, Roschmann's factory mysteriously burns to the ground before any rockets are delivered to Egypt.
