Spy In Space is the 11th Produced episode and the 5th Broadcast episode of the series Fireball XL5.
Fireball XL5 is asked to take over the patrol duty of XL9, which has been attacked and damaged. The crew make their way to the nearest space station, Companion 12, to refuel, but find it empty. Mr and Mrs Space Spy have taken over station and plan to use Venus as a hostage to steal XL5. their ship S.S Thor, was responsible for the attack on XL9. All seems lost until a rocket is placed in the sole of Mr Space Spy's|magic boots, sending him into orbit. Mrs Space Spy takes the S.S Thor to rescue him.
- Although Steve Clearly knows who Boris and Griselda Space Spy are, the crew have not met them before. So this episode must be seen before Flying Zodiac, Convict in Space and Space Pen, in which the villains also appear.
- Just before the commercial break, a real hand is seen when the Space Spies hold the XL5 crew at gunpoint.