An astronaut is killed on re-entry to Earth, but his body is seeded with rapidly-gestating aliens.

A backwoods game warden and a local doctor discover that giant leeches are responsible for disappearances and deaths in a local swamp, but the local police don’t believe them.

Lt. Robin Crusoe is a navy pilot who bails out of his plane after engine trouble. He reaches a deserted island paradise where he builds a house and begins to…