Sure, there was something in her drink, probably Rohypnol, known as "the date rape drug."
Looked to me like Katherine was quite approving of our Nicky finding himself a hot babe. And clearly he didn't know something was going wrong with Katherine. We don't know the circumstances, but I'm betting her assailant got her out of the club without Nicky even knowing she had left.
I thought the ending was awesome: Clearly Katherine was collecting evidence of her own rape. To have the presence of mind and strength of character to do that, well, as they say, that woman has balls!
Anyone else get the little twist with the guy suspected of murdering his "business partner"? The interlocking committment rings? They were actually lovers.
I'm still not sure about the Grissom and Sara thing. To me it just seems un-Grissomlike for him to start a romantic relationship with someone he supervises on the job.