Spies Strike Silently (original title Le spie uccidono in silenzio) is a 1966 Italian-Spanish spy thriller about a secret agent (Lang Jeffries) who investigates the murder of several prominent scientists and uncovers a world domination scheme involving mind control. The film also starred Emma Danieli, Andrea Bosic, Erika Blanc, and Jose Bodalo.
After Professor Freeman's (Umberto Certain) daughter is murdered, secret agent Mike Dunn (Jeffries) is sent to investigate. He discovers that a number of scientists, all working on projects to improve the world, have been threatened, blackmailed, or murdered.
Dunn suspects mind control, and his suspicions are proven correct when he saves another scientist from a brainwashed reporter. Tests reveal that the woman has been drugged with a "hypnotic toxin." Dunn finds a slip of paper on the reporter with an address and foolishly goes there; he is captured by criminal mastermind Rachid (Bosic) and his hypnotized(?) henchwoman Pamela (Blanc). Rachid tells Dunn that he plans on using his toxin to rule the world, starting with turning Dunn into a hypnotized mole within his agency.
Dunn is injected with the toxin but secretly uses an antidote to resist and pretends to be mind controlled. Wandering the grounds, he comes across the hypnotized Grace (Danieli) and frees her with the antidote as well. Grace manages to make a call for help before she and Dunn are captures again. This time, Dunn is really brainwashed and is sent to murder a scientist, but he is stopped and freed from Rachid's control. They agree to fake the professor's death so that Dunn can lead the authorities back to Rachid's lair.
British secret agents arrive at Rachid's compound, where he is subjecting Grace to a more intense version of mind control involving a brainwashing ray that doubles as an incineration ray(!). Luckily the ray takes 48 hours to brainwash someone while only seconds to set someone on fire, allowing Dunn plenty of time to rescue Grace and roast a turncoat secret agent. They escape, the bad guys are wiped out, and Dunn sends Rachid to his death in a fiery car crash.