The crew of the joint British and American space shuttle the ''Churchill'' finds a 150-mile-long spaceship hidden in the Coma (cometary) of Halley's Comet. Inside, the crew discovers hundreds of dead bat-like creatures and three naked humanoid bodies (two male and one female) in suspended animation within glass containers. The crew recovers the three aliens and begins the return trip to Earth. However, during the return journey, mission control loses contact with ''Churchill'' and a rescue mission is launched to investigate.