Watch the Beginning Again!

I just watched it and rewatched the beginning. All five are there, just discovering Anne's body and her wrist is already slit.
This is before we see the "flashback" of them setting up Vince.
It makes no sense.
Unless---the first version is Luke's (untrue) account to the police of that morning's events.

What do you mean, the next morning? Isn't the timeline all one day? Luke 'discovers' Sarah after she ODs, calls in the 3 guys and they make the plan to frame Vince. Then they disperse to make their alibis, and Luke calls everyone again, including Vince this time and they pretend they know nothing about what happened. This is when all the stuff at the beginning happens, which finishes with them drugging and handcuffing Vince to the girls body. I didn't think he ever got free. I don't know if the movie specified what prompted the police to go to the loft in the first place though, anonymous tip maybe.

In the beginning of the movie we we see Luke "discover" her body and her wrists are already slit. We see this account of what happened while Luke is being interrogated by the police. It's an early an false version given to the cops before they start confessing the truth.

It goes a little something like this......

1. Luke kills Sarah in a jealous rage then writes the fake suicide note
2. He then tells the others that Vince is banging everyone after showing them footage
3. They hatch a plan to set him up (this was silly, made no sense) and Philip slashes her wrists
4. Luke calls Vince round
5. All the rest show up
6. Luke steal suicide note from Chris
7. They all then decide to drug Vince and tell him their plan and handcuff him to the body (this I have no idea why, presumably to ruin his marriage?)
8. Presumably the police find Vince handcuffed to the body and question him for murder.