Scientists discover indications, from widely disparate primitive civilizations, pointing to humanity having been visited - and perhaps, created - by an alien race, called 'The Engineers'. Decoding their source, a spaceship, funded by the Weyland Corporation, is dispatched to what is believed to be the Engineers' home planet. The expedition includes archaeologist Elizabeth Shaw (Rapace), android David (Fassbender), Weyland employee Meredith Vickers (Theron) and the ship's captain. Janek (Elba). On arrival, they find evidence that the Engineers were there, but aeons ago, and there's nothing apparently left of them now except for long-dead corpses. There are, however, a large number of storage cylinders, from which is seeping a dark liquid. Assuming you're aware that this is something of a prequel to Alien, I probably need not say too much more about how things progress from there. Let's just say, the supposedly-dead planet is nowhere near as lifeless as it seems.
It's likely this foreknowledge which makes the first half feel overly long: the audience is well ahead of the characters, who have to learn all the stuff which the viewers already know. It's almost a repeat of Alien in this sense: one of the reasons why Aliens was superior, is that it could discard much of the exposition, since we already knew what we were facing. While there are some variations on the theme here, the basic principles remain, and the movie would have been better off arriving on the planet sooner into the 124-minute running time than it does. That said, this is a Ridley Scott movie and, as always with his work, even if the storyline isn't progressing, it's still visually stunning (even in 2-D, rather than 3-D, as filmed). The second half is considerably more interesting, with a couple of genuinely squirm-inducing sequences and an escalating sense of chaos and despair. The film has been accused of being over-complex or too cerebral. I can't say I found it to be either, and as a muse on what it means to be human, it's a long way short of Blade Runner. Then again, so are almost all movies, so don't hold that against this.