When an Alien Limpet UFO causes the destruction of Lunar Module 32, Straker demands a clean-up programme by the International Astrophysical Commission to remove hazardous space debris from Earth orbit. But Straker finds himself butting heads with I.A.C. chairman James Henderson, who wants a complete shut-down of SHADO operations...

Straker gets approval from above to build a probe with a camera that will track a UFO back to its home planet. Inexplicably, the Earth technology is capable of following a UFO travelling 8 or 9 times the speed of light and follows it home. The episode ends with a SHADO guy trying to convince Straker that they were wasting their time, even though they picked up some great pictures of the planet.