The Body Stealers

The paratroopers were being abducted by aliens as part of a plan to repopulate their plague-ravaged home planet, Mygon. The aliens were kidnapping humans who had spaceflight training, apparently selecting them because their bodies were already adapted to handle the physical demands of space travel and living in a non-Earth environment.

Earlier in the investigation, Dr Matthews notes that all missing troopers had received spaceflight training, hinting at a specific selection criteria beyond random victims.

Lorna is an alien companion of Marthus who was sent to Earth as part of the repopulation mission. She possesses the ability to mimic human appearance, which explains why she could appear at the laboratory and then vanish without trace. Her vanishing acts were a result of her alien physiology and the need to avoid detection while assisting the abduction operation.

Megan notices that Lorna leaves behind more questions than answers each time they meet, and her mysterious behavior contrasts with the other human characters at the facility.

One abducted trooper was recovered in a critical state and died upon arrival at the military laboratory. Dr Julie Slade performed an autopsy and discovered that the man's biochemistry had been significantly altered, revealing that the aliens were experimenting on or adapting the humans for survival in a non-Earth environment.

The investigation initially focuses on finding a pattern, and this discovery of altered biochemistry confirms that something beyond normal military operations was happening.

Dr Matthews theorizes that the aliens selected troopers with spaceflight training because their bodies were already conditioned to survive in extreme conditions and non-Earth environments. This made them ideal candidates for the alien repopulation plan, as they would have a higher chance of surviving on the plague-ravaged planet Mygon.

Early in the investigation, Megan learns all missing troopers had undergone spaceflight training, creating a puzzle that connects to the alien motive.

Marthus killed the real Dr Matthews and took over his form and identity, using his ability to impersonate humans. This allowed Marthus to operate within the military laboratory undetected while directing the investigation away from the truth. When Megan traveled to Matthews' cottage, Slade discovered the real Matthews had been killed and replaced.

Dr Matthews seems unusually cooperative and theorizes about alien involvement early on, which makes more sense once his true identity as Marthus is revealed.

Marthus explains that his home planet, Mygon, was devastated by a plague that killed most of its population. The aliens are kidnapping humans to repopulate their world, essentially using abducted humans as breeding stock to rebuild their species. The human bodies are needed because the aliens require human physiology to survive and reproduce on their dying world.

The mysterious disappearances and the aliens' interest in human physiology become clear once the full scope of the repopulation mission is revealed.

Mygon is the aliens' home planet, which suffered a devastating plague that nearly wiped out its entire population. The alien duo of Marthus and Lorna were sent to Earth to abduct humans and use them for repopulating Mygon. This explains the scale of the operation and why they specifically targeted humans with spaceflight training who could potentially survive the journey.

The aliens' need for humans becomes clearer when they reveal the scale of their mission and why they needed volunteers for the repopulation effort.

Lorna intervenes to incapacitate Marthus when he attempts to kill Megan and Dr Slade, revealing herself as his alien companion. While she still supports the repopulation mission, she chooses not to let Megan and Slade die. Later, she agrees to Megan's bargain to return the troopers in exchange for volunteers, suggesting she prefers a cooperative approach over violent coercion.

Lorna's mysterious behavior throughout the investigation, including her repeated disappearances, hints at a dual allegiance that becomes clearer in the confrontation.

Lorna reveals the troopers are being held in suspended animation aboard the alien spacecraft. Megan negotiates a conditional exchange: if Lorna returns the troopers, he will help find volunteers to assist with the Mygon repopulation effort. Lorna agrees and vanishes with Marthus and the spacecraft, leaving the immediate crisis resolved but the larger question of human-alien cooperation unresolved.

The ending leaves ambiguity about whether Lorna will actually return the troopers, though she agrees to the bargain proposed by Megan.

The aliens used their spacecraft and advanced technology to intercept the paratroopers during their routine jumps. The summary indicates they had a spacecraft capable of facilitating their travel between Earth and Mygon, and they used their ability to mimic human form to operate undetected. The precise method of capture isn't detailed, but it involved extracting humans from the sky mid-parachute.

The investigation reveals disappearances happen specifically during jumps, suggesting the aliens could track and intercept airborne targets.