Goodbye Catherine!
There have been a major change to CSI in the past few weeks. Catherine's gone! She left for a job at the FBI (after an attack on her killed her friend who was in the FBI). This happened in the episodes "weeping in the willows parts 1 and 2"
So Catherine's gone, and everyone's missing her. Hopeflluy there will be collaberations and joint investigations between CSI and the FBI, so we can still see Catherine.