 Halley s Comet returns to the solar system and the English/American team aboard the shuttle "Churchill", making a close-up survey of the comet, discovers an alien spacecraft in the head of the comet. Inside the spacecraft are some large bat-like creatures and in three cocoons are three "dead" humans - two men and a woman. The "Churchill" takes the humans and a creature back to Earth. There the bosses of the project are amazed to find the shuttle burnt out and all but one of the crew - Carlsen - dead. The humans from the spacecraft suddenly awake and all those who come into contact with them are drained of their "lifeforce" and in time all the victims - including most of the population of London - are turned into zombies all praying on the horrified survivors for their "lifeforce". It s up to Carlsen and Major Caine of the SAS to stop them before the whole world turns into a big blood-hunt...