Following a triple professional hit a U.S. agent, Paul Sherman, arrives in Amsterdam to investigate a heroin smuggling ring. He finds a city rife with drugs and a police force unable or unwilling to do much about it. With his incognito female fellow agent, Maggie, the American is soon stirring things up.

Based on the medieval legend of Pope Joan, who was made Pope for a brief period around 855 A.D. The movie presents her existence as fact, though it is questionable that Pope Joan really did exist, and portrays her relationships with other notables of the time.