A film is found that features Kurt von Metz helping Adolf Hitler commit suicide. Years later, von Metz, running for chancellor of West Germany, arranges for anyone who has seen the film to be murdered. The killings take place in the Washington D.C. area, and Metropolitan Police officers MacArthur "Mac" Stern and Ellis Fielding are sent to investigate the crimes.
Ellis suffers from a dissociative identity disorder stemming from a disastrous undercover drug sting, which is aggravated when he is confronted with violence. This results in several episodes where he blacks out and assumes the personalities of pop-culture characters, including Popeye, Captain Kirk and the Road Runner.
Mac and Ellis attempt to track down the film through pornographer Harry "The Hippo" Gutterman, who informs them that to do so they need to get to New York City. They decide to take a train, but first must evade a team of FBI agents led by Bob Smiley, who must shield von Metz from embarrassment by intercepting the film before it goes public. They all meet up at Washington's Union Station, where Mac and Ellis trick Smiley and his team into boarding the New York-bound train they originally intended to take, while they jump off and hop onto one on the opposite track bound for Cleveland instead. While on board that train, Mac notices another undercover team that has been trailing them, which is revealed to be led by Rebecca "Riva" Lohengrin, a Mossad agent assigned to the Embassy of Israel in Washington, D.C.
After surviving a helicopter attack on the train by Nazi sympathizers, Mac, Ellis and Gutterman jump off a bridge into a river and eventually make their way to New York. En route, Ellis confides in Mac his fear that if another episode occurs it could prove irrevocable, which would make him a dangerous liability, and wishes to return to the Benedictine Monks who originally looked after him during his recovery. Mac, however, reiterates his belief in Ellis and shows him that he is strong enough to persevere, move forward and recover; that the past is irrelevant and that the present and the future are what matter.
Consequently, Ellis regains his courage and the will to fight. Mac finds the film in a locker on one of the upper levels of Grand Central Terminal and, during an exchange of gunfire with more Nazis, throws the film to Riva, who has just arrived on the main concourse below. It is screened that same evening during a speech that von Metz delivers. Mac, Ellis and Gutterman all suffer gunshot wounds and, as the movie ends, are seen recuperating in the same hospital. Mac jokes to Ellis that he is converting to Judaism that evening in order to move to Israel to join the Mossad but is uncomfortable about undergoing circumcision. Ellis catches on to the humor and points out that the reason that they work together so well as partners is because technically, Mac is crazier than he is.
