Space Brain

A spatial anomaly jams all of Moonbase Alpha's communications with hieroglyph-like symbols. Eagle 1 is launched to investigate the swirling object, which the pilots liken to a giant anemone. On approach, the Eagle is covered in glutinous strings and contact is lost. As a rescue Eagle is launched, a small meteorite hits the Moon. It is coated in the same gel-like substance, which Dr Russell's analysis shows to be organic. Professor Bergman reports that the meteorite's components are those of an Eagle – with traces of human tissue. Commander Koenig realises they have recovered part of the crushed remains of Eagle 1.

Rescue Eagle co-pilot Kelly is conducting a spacewalk of Eagle 1's last known position when he is transfixed by the anomaly. The unconscious astronaut is retrieved by Captain Carter and returned to Alpha, where Russell discovers that his brain has gone into overdrive. Alpha's computer starts downloading data into Kelly, which his brain relays to the anomaly. Using the astronaut as a conduit, the anomaly responds by flashing more symbols on nearby video monitors. The Alphans deduce that the anomaly is a living organism. Kelly breaks out of Medical and attempts to reprogram Computer, but is thwarted when Koenig cuts the power. He collapses in the arms of his wife Melita, begging her to "make them understand".

The Moon is heading for the anomaly and the same fate as Eagle 1. With no way to alter course, the Alphans plan to weaken the anomaly by remotely flying nuclear ordnance into its core. As the bomber Eagle departs, Bergman discovers that the gel has turned into a super-dense foam. The information that Kelly transmitted was about the Moon, including its course changes since it broke away from Earth. Koenig believes that the anomaly is benevolent and, like the Alphans, wants to avoid a collision. He has himself neurally linked with Kelly and learns that they are dealing with a vast "space brain", perhaps the lynchpin of whole galaxies. The material that destroyed Eagle 1 is the brain's equivalent of antibodies, evolved to fight invading pathogens. Were a Moon-sized body to fall through the brain, the immune response would be on an entirely different scale.

Speaking through Kelly, the brain proposes detonating nuclear warheads around the Moon's equator to affect its rotation, and possibly its trajectory. Needing to recover the ordnance they sent up, the Alphans attempt to recall the Eagle, but the autopilot fails. Flying a second Eagle, Koenig docks with the bomber and defuses the payload, but the return journey ends disastrously when the bomber breaks free and crashes on the Moon.

The back-up plan is to increase Alpha's atmospheric pressure and seal off its sections to repel or contain the antibodies. Non-essential personnel are moved to subterranean shelters, while those who remaining above ground put on spacesuits. The Moon enters the brain and is submerged in torrents of foam. Alpha's Medical section is breached and Kelly is killed. Main Mission is flooding when the Moon passes out the other side, ending the bombardment. Speculating that their transit has probably killed the brain like a bullet through a head, Koenig and Russell lament their failure to establish meaningful communication and understanding.

Principal photography at Pinewood Studios took place between 5 and 19 December 1974. The alien antibodies were represented by shaving foam in the special effects sequences, and a mixture based on sodium dodecyl sulphate in scenes with live actors.^[1]

On the making of the foam-filled climax, Nick Tate remembered that the sets became treacherously slippery and the noise was deafening because of the aero engines that were being used to drive the foam. He recalled: "[T]his twelve-foot wall of foam, which was as scary as if it had been a real menace, came floating down the studio floor, about a hundred yards wide. We were all dressed up in our spacesuits and had to wade through it [...] [The director] went rushing out in front of the cameras waving his arms and screaming, 'Cut! Cut!' He hit the base of the foam, shot underneath it like in a Laurel and Hardy movie, and completely disappeared. When he finally struggled out, he looked like the Abominable Snowman."^[2] Tate reflected that the filming process was "very amusing, but at the same time very dangerous."^[3]

According to Barry Morse, the climax was filmed in two takes, shot many hours apart "because no one had thought how we were going to get all these soap suds out of the set." He added: "[B]y the time we came to take two, we realised that we could not stop for anything." As the second take began, the clapper loader fell into the foam, but delayed picking himself up so as not to ruin the shot. "[W]e went on playing this wretched scene whilst he was being smothered by the soap suds and foam, scarcely able to breathe."^[4]

By the end of filming, Gerry Anderson, the series' executive producer, was dissatisfied with Christopher Penfold's script. He decided to revise the plot to make it clearer that the "space brain" was a friendly entity, while adding in several new scenes. Filmed over three days in February 1975, Anderson's additional material was the last to be shot for Space: 1999 Series 1. The rewrite included a new cold open with an off-duty Commander Koenig finishing a jigsaw puzzle based on a painting of the Visitation of Mary. Because Carla Romanelli was no longer available, the role of Melita was re-cast.^[5][1]

A scene cut from the finished episode showed the mesmerised Kelly trying to hijack the Rescue Eagle, forcing Carter to stun him with a laser weapon. The climax is set to a 1957 rendition of "Mars, the Bringer of War", the first movement of The Planets by Gustav Holst. The episode also features incidental music originally composed for Joe 90 and The Secret Service.^[5][1]