Tasked with investigating the kidnappings and brainwashed reappearances of top scientists, including Dr. Radcliffe (Aubrey Richards), the insubordinate British spy Harry Palmer (Michael Caine) navigates his way through criminals, secret agents, and his superiors (Nigel Green, Guy Doleman). While attempting to bring in the suspect Bluejay (Frank Gatliff), Palmer discovers a mysterious audiotape labeled IPCRESS, an inconspicuous, but ominous, piece of evidence.