After several cases of random suicides, an investigation into the latest one leads Captain Blue to inadvertently upload a virus to Skybase's computers. Everyone on the base apart from Captain Scarlet and Destiny Angel are infected by the deadly virus which makes people end their own lives. Scarlet and Destiny must erase the virus before they too become infected.

The Mysterons threaten to kill one of Spectrum's Angel pilots.

The Protectors find themselves in the middle of a war over some antiques.

Rocky has a toothache, but nothing anyone says can persuade him to have his tooth removed by Doc Haggerty.

The Moon is on a collision course with an enormous planet. On a scouting mission, Koenig encounters Arra, the Queen of Atheria. The aged monarch proclaims the collision is a preordained event and must occur for her people to evolve to a higher plane of existence. Now Koenig must convince his crew to have faith and do nothing in the face of apparent destruction.

A malfunctioning solar reflector menaces the Italian coastal village of Monte Bianco, where Lady Penelope and Parker happen to be visiting while on holiday.

The Stingray crew investigate a disused lighthouse emitting unexplained signals.

As part of a criminal operation to seize £1 million in bank notes en route to London, the train carrying the shipment is diverted to the disused Buffler's Halt Station. Unwin and Matthew help to subdue the gang responsible. However, on the way back up the line, stationmaster Albert Hobson realises that he cannot stop the train, which is travelling at 80 miles per hour.

SHADO officially goes into operation and encounters its first UFO. An alien pilot is captured and discovered to have transplanted human organs within him.

Clip show episode: Joe reaches his tenth birthday, and celebrates with his friends as they reminisce over his many adventures.