Voyeur

 Peter sits at the bar and listens to a couple of guys discussing the brunette sitting not far away. He has to agree she does look easy, the way she's dressed, short skirt, loose top with no bra... it's like she's inviting their crude observations. Soon the action hots up as they invite her for a drink and discover that she really is a slut. 

Shocked and horny... Peter watches the fun unfold!