"In the blink of an eye, the terror begins..." LifeForce was a science-fiction flick based on a 1976 novel titled The Space Vampires. During its release, the movie received mixed reviews, and it turned out to be a dud at the box office. The movie starred Steve Railsback as Colonel Tom Carlsen, Peter Firth as Colonel Colin Caine, and Patrick Stewart as Dr. Armstrong.
The movie beings with a space shuttle crew on the way to investigate Halley's Comet, where they find a huge alien spacecraft hidden in the comet's corona. Once boarding the alien vessel, the crew finds many dead bat-like creatures, and three humanoid creatures in suspended animation that they bring back to the shuttle. Something goes wrong during the return trip, and all put the alien pods is destroyed. A rescue mission finds the pods, and the alien humanoids are brought to earth. During the autopsy of the female alien, she wakes up and begins killing scientists by draining out their "life force".
It turns out that the aliens are essentially shape-shifting vampires, but instead of blood, they require the life force, and once bitten, victims also turn into vampires who must feed on the life force or perish. It just so happens that one of the original astronauts managed to escape in his space pod, so he is brought to help out. Well, things go from bad to worse, and eventually the entirely of London is plagued by the infestation. The bad news is, at the end of the movie, with London a wreck, the vampires manage to get back to their ship and escape.