I think Catherine appears 90% in this episode. This episode is full with Catherine's drama, where she met a man in the club who hits her. Then after that, a blonde lady is found dead and went to the same club where Catherine was.
This is a filler episode. Lacked of scientific investigation. Wasn't the full name of CSI is Crime Scene Investigation and it is suppose to be a show about forensic scientist. But this episode is a little similar to Criminal Minds instead of solving the crime by scientific investigation by forensic scientist. However, this episode is still good. Good plot, good directing, but please, more scientific investigation.