World War II is over, and Nazi officials remove Adolf Hitler's living head and hide it in the fictional South American country of Mandoras, so that they can resurrect the Third Reich for the future. Fast forwarding into the 1960s, the surviving officials kidnap a scientist in an attempt to keep Hitler alive. Various intelligence agencies, aware of the evil plot, recruit secret agents to bust the Nazi officials.

References:
https://en.wikipedia.org/wiki/They_Saved_Hitler%27s_Brain