So, David is *genuine spoiler*

If anyone has resisted the urge to read the plot synopsis, you can get away with reading halfway through it and still keeping two-thirds of the surprises for when you see it on screen. There's a plot summary on wiki now if you can't find it anywhere else. *SPOILER* But as it turns out, David the sneaky bugger swipes an ampule of alien stuff from the temple and smuggles it back onboard the Prometheus. Then, he gets a message from Weyland telling him to infect Holloway with what he finds inside. Vickers catches wind of the message but doesn't know what David was told and doesnt know what to expect (that clip we've all seen). So, David infects Holloway, Holloway bones Shaw (impregnating her with an alien), and Holloway shows symptoms during the next visit to the temple. I'll save the rest for you to find out for yourself. David is an antagonist as it turns out; did anyone else see it coming?