It's a surprise that Benson slept with her colleague when she's called in for a rape incident. We didn't see them in chemistry in earlier episodes. Benson meets rape victim, Harper Anderson who claims the suspect used a weapon with the line, "Is this how you like it?". But, there's no clear evidence
after one suspect is ruled out. A few months later, Benson hears about a similar incident from a detective from another precinct saying the guy attacked her with a mask. Then, the squad finds a married man, who happens to be wearing the victim's ring. Benson tries to bring in Harper, but discover she's moved on with her life and refuses to do so. But, Benson talks her out of it and decides to face the suspects. Then, Harper is unable to pick out the guy and breaks down when she sees her stolen ring.
That was emotional. The emotions the victim has to go through is good. It didn't make sense with the sexual tension with Benson and Cassidy. There was a little backstory that they got smashed and had sex. But, Benson made her mistakes. Cassidy wants commitment. That was emotion right there. I even saw that guy from 'White Collar' playing her boyfriend.