The show opens with a man demonstrating a remarkable incomprehension of the "no means no" rule. The woman wriggles out from under him and manages to smash him upside the head with a water glass and runs into another room, closing the door behind her and blocking it with a dresser while her attacker pounds and yells.
She calls 911, and the next thing we know, Olivia and Elliot are interviewing her -- Christie. Her attacker was her sister Rachel's boyfriend, Dan -- it's their apartment. But Rachel's nowhere to be found, and the blood in the room and by the fire escape indicates she didn't leave willingly. Meanwhile, a much calmer Dan seems shocked to hear what he's being accused of. His excuse? He was sleeping while he did it.
Elliot grills Dan, who's maintaining that he's got arousal parasomnia (also called sexsomnia). Oh, and he offers a little too much information when he tells us that Rachel says the sex is best when he's asleep. Dan's lawyer backs him up. You're never going to believe this, but Elliot is a little bit skeptical, especially since the lawyer's contention is that Dan can't be charged since he didn't have any idea what he was doing.
But Casey confirms that's the case. Dan's going to walk, and apparently the detectives aren't going to even require medical evidence of this condition? There's also the matter of the missing Rachel McGarrett; Dan says he woke up when Christie knocked him with the glass went running into the bedroom, but Rachel was already gone. Huang finds this believable; his feeling is that in Dan's condition, he wanted to have sex, but Rachel wasn't there so he went for Christie. The detectives are thinking Dan killed Rachel and then went after Christie, but Casey says there has never been a case of sexsomnia linked to a homicide (way to prevent all the angry phone calls to NBC from sexsomniacs pissed off at the depiction of their problem). Huang does think, however, that if Rachel did love Dan (as both Dan and Christie have said during questioning) she's not likely to leave in the middle of the night; Huang thinks she was kidnapped.
After all this time, you'd think the detectives would co-ordinate a little better so they aren't escorting a victim out of the detachment at the same time they escort the guy who did it. Dan tries to apologize, and Christie wants nothing to do with him, and she goes running into the arms of her father, who just showed up. Daddy tackles Dan and gets in a shot or two before the ridiculously slow-reflexed Olivia and Elliot can pull him off. Mr. McGarrett reacts about as well as you'd expect to the news that no one's going to be held responsible for the attack on his daughter. Good thing he doesn't ask a couple more questions, because maybe Olivia and Elliot would have to admit that the only proof of Dan's condition is his word and the word of his lawyer.