A joint space mission between the United States and the United Kingdom leads to the discovery of a strange alien spacecraft hidden in the tail of Halley's Comet. The crew, upon investigating, finds three humanoid figures in suspended animation: two male and one female. They decide to bring these beings back to Earth, but communication with the shuttle is soon lost. The shuttle returns to Earth's orbit, where it is intercepted by a rescue mission which finds the crew dead save for one body, the female alien, still in her preservation chamber.

The recovery of the alien bodies from the shuttle catastrophe in Earth's orbit sets off a chain of mysterious incidents. The female alien awakens in a London laboratory, revealing herself to be a life-sucking space vampire. Her energy-absorbing kiss leaves her victims desiccated husks, which in turn become vampire-like creatures hungering for the life force of others. As the contagion spreads and chaos ensues, a race against time develops to understand the true nature of the alien threat and to find a way to stop the growing epidemic before it decimates all of humanity.