Grissom has been promoted from senior officer on the graveyard forensics shift to head of the Las Vegas Criminalistics Bureau. An investigator of the old school, with 17 years on the job, Grissom eschews computer simulations and readouts for hands-on technique and legwork. CSI is his life. He supervises a team of very diverse professionals, and often goes to the wall to protect them from department interference - and sometimes, from the consequences of their own risky decisions, on and off the job.

A single parent with a young daughter, Catherine's a street-smart Las Vegas native, a veteran criminologist who juggles the job she loves with her responsibilities at home. The horrors of the crime scenes Catherine investigates bring into sharper focus her fears for her child, making her even more determined to shield her little girl from the seamier, shadowy side of Vegas that is revealed after the sun goes down.

Warrick Brown has got innate talent and drive, but his fortitude is frequently misconstrued as cockiness. He is always striving for more - both on the job and in his personal life. Dealing with a gambling problem and some questionable decisions he has made, Warrick has a lot prove, to both the CSI team and himself.

Equal parts charm and chops, Stokes was more than happy to take Warrick Brown on in a friendly competition to reach the level of CSI-3. With his 100th cleared case behind him, Nick is self-assured and focused, yet not above being teased by his colleagues by his revolving-door reputation with women. He's very serious about this job, and does it well, but Grissom still rides him to be better.

The newest member of the CSI team, Sara is a sharp, no-nonsense investigator out of San Francisco who sometimes colors outside the lines in order to close a case. A friend and former student of Grissom's, Sara comes to the CSI team ready to challenge the others, and though she expects some resentment from the team, she demands their respect, and does not care how long it may take to get it. Although her brash manner doesn't always gel with the human element of her job, Sara makes a concerted effort to become more empathetic.

The former boss at CSI, Brass has been shifted back to homicide. This puts him at odds with Grissom, and often puts him back at the crime scene with members of the team he used to supervise. The detectives and the investigators all want the same things, but sometimes their good intentions - cop vs. scientist - collide.