Steve attemps to relocate a hugh crocodile to save him from poachers. But what Steve doesn't know is that the big croc has swallowed a top-secret U.S. satellite beacon ... making them both targets of the U.S. special agents assigned to retrieve the beacon.

Doctor Who, Harry and Susan accidentally land on an artificial satellite where they discover people from Earth suspended in a frozen state. The bad news is that they also find a dead insect, the queen of the Wirrn, sworn enemies of Earth. The Wirrn's egg sac is full, so the good Doctor must destroy the larvae before they absorb the last of the human race.