Best Investigation movies of 1964

Actors : Sabine Sesselmann, Elga Andersen, Heinz Drache, Ralf Wolter,
Directors : Manfred R. Köhler,

A private detective finds the limp body of a young Chinese beauty in his office, shot with his own gun.

Actors : Paul Klinger, Judith Dornys, Heinz Drache, Ingmar Zeisberg,
Directors : Rudolf Zehetgruber,

A private detective tries to find out how and why some convicts have mysteriously disappeared from the prison of Dartmoor.

Actors : John Hoyt, Arlene Martel, Elisha Cook Jr., Bob Kelljan,
Directors : Antonio Santean,

Two detectives investigate the murder of a local businessman by a mysterious woman.

Actors : Diana Martín, Bernard Price, Claude Dantes, Tony Kendall,
Directors : Gino Mangini,

A serial killer called "The Hyena" is finally caught and eventually hanged. However, his body disappears before it can be buried, and soon thereafter dead bodies start turning up in a small village.

Actors : Roland Carey, Maria Grazia Spina, Mario Feliciani, Gabriele Antonini,
Directors : Guido Malatesta,

A roman consul is sent to Gaul to investigate the theft of gold shipments. He discovers that the gold is being stolen by a tribe of barbarians--whose leader is the governor of Gaul.