Moonbase Alpha is plagued by intermittent disturbances. Commander Koenig keeps having nightmares in which the ghost of a woman accuses him of killing her. Meanwhile, technician Sally Martin, devastated over her broken engagement, is inventorying stores when she is crushed to death by a sourceless wind. Suspected of her murder are her ex-fiancé, Mark Sanders, and his new lover, Carolyn Powell. Powell comes under increased suspicion when she is found to have been experimenting with a device that can project pressure waves. The Moon approaches a gaseous formation filled with electrically-charged particles. In the recreation room, Carl Renton, known for his bad luck, has won 17
games of chance in a row. His opponent accuses him of cheating and they come to blows. Elsewhere, the Eagle fleet is grounded by malfunctions. After speaking with frustrated engineer Pete Garforth, Captain Carter finds himself locked in the workshop. An atomic device starts up, threatening to explode until Maya, who happens to be passing, shapeshifts into a gorilla to break into the room and deactivate it. Koenig tells Dr Russell the cause of his nightmares. Years earlier, he was part of a team that arrived at a space station to find its crew dead from an alien disease. To contain the infection, the station was quarantined – but Koenig's friend Sam, and Sam's fiancée Tessa, had already been exposed and were left to die. Back in the present, Sanders tells a distraught Powell that their relationship is over. Later, he is hit by a blast of air and his body pulped, while Powell watches. Instruments detect electrical activity resembling "lambda"
brainwaves. Russell identifies these as the lambda
variant: a rare pattern known to
parapsychologists. It is creating above-average
psychic powers in most of Alpha's population. Three individuals – Renton, Garforth and Powell – demonstrate exceptional ability with the potential to harm others. Believed to include Martin and Sanders' killer, the three "sensitives" are placed in a force field strong enough to block out the variant. Powell is the only one who continues display paranormal ability, which she reveals by breaking out of the force field. She takes over the Command Center and psychically tortures the staff. Sam and Tessa are now terrorising Koenig during his waking hours, leaving the commander
catatonic. Using
narcosynthesis, Russell revives Koenig and helps him come to terms with his repressed guilt. Koenig forgives himself and the spectres, created by his psi powers, disappear. For the sensitives, the variant has amplified hidden aspects of the psyche. Renton's power allows him to manipulate gaming odds to his advantage; Garforth's exploits his
fear of flying to compel him to sabotage the Eagles; and Powell's turns her feelings of inadequacy into a killing force. Koenig, the only Alphan of equal paranormal strength, confronts Powell. As they engage in a wordless battle of wills, a vortex of wind fills the Command Center. Starved of negative emotions, Powell is defeated and her mind emptied; now as innocent as a newborn, she will have to grow up again. In space, the gaseous formation vanishes. ==Regular cast==