Boy and girl are talking.
New girl joins the group and kisses boy on lips. (her boyfriend)
Boy asks new girl 'where have you been?'
As she answers, we cut to the dialogue playing over the footage of her evening.
After she finishes, it cuts back to the group in the alley.
New boy arrives and kisses the first girl. (his girlfriend)
The first girl then asks 'Well what took you so long?'
He answers, we cut to the dialogue playing over the footage of his evening.
New boy afterwards asks original boy and girl 'So hows the party?'
They answer together explaining their night and we cut to the dialogue playing over the footage of their evening.
The footage though is slightly off what they are actually saying and we end with them fucking in the toilets. (possibly could tie this idea in with the couple fucking in Alex's idea)
Footage then cuts back to the group in the alley and we leave them in silence with their partners oblivious to being cheated on.