What I think will happen in the movie....

...just adding my idea based solely on what I've seen in the trailer. Bearing in mind there are a lot of shots out of sequence in the trailer... For whatever reason, the crew of the Prometheus head out to explore the Alien structures on the alien planet. Dunno why they go - but i don't think it's a distress beacon thing - Ridley's done that once already in the original Alien and i reckon he won't use that ol' line again. One thing is clear to me, there are NO Engineers left alive...everything is derelict. They explore the derelict and find the 'star chart room' - amongst other things. Obviously, they find the room with the human head statue and the ampules. Now, as the tagline suggests, the crew think this points to the beginning of mankind ('they went looking for our beginning'). However, upon disturbing the ampules as they try to remove them for study, they set off alarm systems etc and one of the guys gets 'infected' by whatever's in the ampule. Now, this is where it gets interesting....the crew at first think that the ampules are responsible for mankind's existence, BUT they're actually designed to mutate humans into more Engineers - this is how the engineers propagate I think. So, they all race back to the Prometheus, and the chap who got 'infected' starts to mutate and turn against the humans - probably so he can try and mutate them too (possible by incapacitating them and taking them back to the ampules - a bit like the Alien drones do in the other films). We then see this mutant human in the star chart room/bridge/telescope room. We see him here mid-mutation. He's far bigger than a human, the bridge of his nose seems weird - sort of halfway between human and the snorkel style nose of the Jockey. He then fully mutates and enters the telescope chair and tries to take off in the ship. His destination is Earth, where he plans to infect all human life and turn them all into Engineers. The captain of the Prometheus takes off, leaving Shaw and the other one on the ground. He crashes into the alien ship in a suicide attempt to ensure the ship and it's deadly cargo can't make it back to Earth. The Prometheus crew thought they were discovering the origin of mankind, but they stubbled across a dead alien race that can only live by infecting and mutating human life...hence the words at the beginning of the trailer: "You don't understand' , 'we were wrong' and 'I'm so sorry'... ...there we go, hope you followed it ok. It seems to tie in a lot of things ok for me. But one thing that i can't find a reason for is the big circular ship you see over the water fall.... thanks for reading, and go easy on your comments - it's just a bit of fun after all! PS: I'd not seen the belly inflate thing till just, so yeah, the guy who gets infected maybe impregnates Shaw or someone else and either the baby or the original infected human turns into the Engineer. But however it happens - the crux of my argument is that the Enginneers need to harvest us poor humans in order to procreate. They're are none of the left anymore - until one of the crew gets themselves mutated into one of them and tries to kick start the Engineer race again by flying off to Earth to harvest mankind - and that's what the Prometheus crew find out and try and stop.....