The Lost One (German: Der Verlorene) is a 1951 West German crime drama film directed by Peter Lorre and starring Lorre, Karl John and Renate Mannhardt.

[2] The film's sets were designed by the art directors Franz Schroedter and Karl Weber.

Some scenes were shot at Studio Bendestorf and on provisional stages in the former flak tower on Heiligengeistfeld Hamburg, while location shooting took place around the city.

Dr. Rothe (Peter Lorre) is a German scientist doing secret research for the Nazi government during World War II.

The film was unsuccessful with most of the German audiences in the 1950s, who tried to forget the Nazi era and preferred Heimatfilme.