Leave, and go to the bathroom
From Create Your Own Story
You speak up "You two, I need a piss. You sort it out while I'm gone. It'd be a shame for this night to end like this, is all I'm saying."
After putting on your boxers, you open the door and make your way to the bathroom and relieve your bladder, smiling to yourself at how amazing this night has turned out. As you flush, you notice your cell phone is in there, you must have left it there when you introduced Kara to blowjobs, you reason. You collect it, then walk back to the dining area. It's a massive house, which must be the only reason Adam's mom hasn't heard all the noise going on.
Just as you reach the doorway to enter you hear moaning sounds. "Interesting!" You think to yourself. You push the door open a little and see Adam lying back on the sofa while Kara is frantically servicing his cock with her mouth. "Dirty bastard!" you chuckle to yourself.
Take a picture of it with your phone. Blackmail may come in handy one day