SHADO engages in its first battle with the enemy. Sky One cripples an alien ship which crash-lands in a lake. Straker's team capture its pilot, a strange blue-skinned humanoid - and the grim secret behind the aliens' are revealed

After a pilot is killed when Moonbase operatives fail to give him course change information, the personnel are recalled to Earth for an investigation. A UFO crashes in northern Canada and the personnel are assigned to the operation to find the UFO. Gay Ellis is to coordinate the movement of the mobiles trying to approach the UFO.

A SHADO Technician, who is being blackmailed for information by an unknown party, is caught by Freeman, but not before the information is passed. The Technician, Paul Roper, divulges what information he gave to the blackmailers, to SHADO. After much work on the cryptic data, they discover it is part of a plan by the aliens to attack the Moonbase in a way that would be undetectable. Now it's up to Roper to redeem himself, as he is sent on the suicide mission to stop the attack. If he fails, the base will surely be destroyed.

An XV-104 test plane wanders into a UFO target area and the pilot, Paul Foster, makes sightings of both the UFO and Sky One. Angry and frustrated that no one believes his story, Foster suspects a cover-up and decides to conduct his own investigation into the activities of ex-USAF Colonel Ed Straker.

Foster, whose radio is knocked out and his oxygen line cut, is presumed lost (but they did a crummy job, not even trying to find his body) during a confrontation with a UFO on the moon's surface. Foster is found by an alien, and together, they cross the lunar landscape, developing a friendship when the alien must try to do make-shift repairs on Foster's suit to keep him alive. At the end, a Moonmobile crew finds Foster and misunderstands his intent when he points them to the alien nearby. Contributed by GeoffYukon

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...

Two of the SHADO people, dining at a fancy restaurant, begin to recall this event after one of them sees a diner who was part of Dalotek. A private company installed a facility on the moon which discovered an alien device that disrupted Communications between Moonbase and SHADO on Earth. Contributed by GeoffYukon

""Important? What can be more important than your own son's life?"" Straker faces the toughest decision of his career when his son is critically injured in an accident. The drug that can save his life can only be ferried from New York in time aboard a SHADO Transporter - the same Transporter that is in the prime position to track an Alien defector on the West Coast of Ireland

Foster is abducted by aliens from a health spa and is being taken out into space, presumably back to the alien homeworld. However, the UFO was damaged and returns to the moon, crashing there. While the Moonbase personnel try to free Foster of the alien environmental suit, Foster wakes up in the steam room at the health spa. The episode begs explanation for how Foster dreamed in such orderly detail, including Carlin missing a shot and Straker angry at the missed shot, and Dr. Jackson's off-line comments to Straker before they go onto a visual link to Moonbase to guide them through removal of Foster's alien helmet. Contributed by Geoff Yukon

Freeman takes over temporarily while Straker deals with a woman apparently determined to investigate what SHADO is all about.

""Unfortunately for them, an Alien came through that door instead of her husband."" In the woods between Clare Cross and Lingbury, an injured Alien stumbles into a lonely cottage and is shot down by Liz Newton and her lover Cass Fowler. Liz and Cass are taken to SHADO HQ for questioning, but when Liz's husband arrives at the cottage, Paul Foster realises that the Alien's death was no accident!

Foster is suspected of being a security leak, but during the trial, Straker and gang discover that Foster's apartment was bugged and shut down the disreputable business that is selling the spy gear.

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.