The Body Stealers 1969

When British paratroopers vanish in mid‑air during routine jumps, Bob Megan, a former air force investigator, is brought in to solve the mystery. His inquiries take him to a military research laboratory headed by Dr Matthews, where he uncovers a series of puzzling signs. There, he encounters a woman named Lorna who vanishes after each meeting, leaving behind more questions than answers.

One trooper is found barely alive and dies on arrival at the laboratory. An autopsy by Dr Julie Slade reveals that the man’s biochemistry has been altered in unsettling ways. Megan learns that all of the missing troopers had received spaceflight training, a detail that pushes Matthews to theorize that they are being adapted to survive in a non‑Earth environment (a chilling possibility that broadens the scope of the case).

Traveling to Matthews’ cottage, Slade discovers that the human Matthews has been killed and his form taken by an alien known as Marthus. When Megan arrives, Marthus explains that the troopers were abducted as part of a plan to repopulate his plague‑ravaged home planet, Mygon. The revelation casts the mission in a new light, and Marthus makes a push to eliminate Megan and Slade, though he is ultimately incapacitated by Lorna, who is revealed to be his alien companion.

Lorna then shows Megan the troopers, still alive but held in suspended animation, and reveals the alien spacecraft that facilitates their travel. Megan voices a fragile bargaining that if Lorna returns the troopers, he will help assemble volunteers to assist in the Mygon repopulation effort. Lorna agrees to the exchange and vanishes once again, taking Marthus and the spacecraft with her.