CSI Det. First Grade: Mac Taylor (Gary Sinise): is leader of the CSI team. He was born in Chicago and even considered working for the Chicago Police Department. The death of his wife, Claire Conrad Taylor, in the 9/11 attacks troubles him to this day, causing chronic insomnia. It was also notedin the first season that he kept a beach ball in his closet that oncebelonged to his wife. He stated he was unable to throw it away becauseit contained some of her breath. He served as a lieutenant in theUnited States Marine Corps, once saying that he had wanted to serve thecountry more than anything else in the world. He served in Beirutin 1983, from which he still bears a scar over his heart. Mac willprotect three things at any cost: the honor of his country, the safetyof his city, and the integrity of his lab. This is why he chose to fireAiden Burn (see below) after she tampered with evidence. Mac has a close friendship with Stella Bonasera. Mac plays the bass guitar at jazz clubs during his off-time. This talent was discovered by Lindsay Monroewhen she observed, during an investigation, that he knew how to holdthe instrument. In season three, he is revealed to have been dating Dr.Peyton Driscoll, played by Claire Forlani.He also met the son that his late wife, Claire, had given birth toyears before they met, only after the boy, now a teenager named Reed Garrett,was found to be shadowing Stella, thinking that she was Claire. InSeason 4, Mac starts receiving mysterious phone calls at exactly 3:33am. Later on, he also realizes that the phone calls come from a numberknown only as 333. To make matters worse, later on in Season 4, Macreceives a letter from Dr. Peyton Driscoll stating that she decides to stay in London and not come back to New York.In Episode 5 ("Down The Rabbit Hole"), he seems to have sleepingproblems and told Det. Don Flack about accepting Peyton's decision tostay in London.In ("Hostage") he is held hostage in a bank by a robber named Joe andthen wakes unconscious in a submerged car underwater in the fifthseason premiere ("Veritas") in which he survives and later captures Joe.

CSI Det. First Grade: Stella Bonasera (Melina Kanakaredes): is devoted to her job due to her strong personality, determination, and intelligence. She is a half-Greek, half-Italianorphan,who grew up moving throughout foster homes. Since they co-head the lab,she is very close to Mac, and constantly worries about his physical andmental well-being. In episode 221 ("All Access"), Stella was heldcaptive in her own home by her unstable boyfriend, Frankie Mala, andwas forced to kill him. Because of her close relationship with Mac, shewas mistakenly thought to be Mac's late wife, Claire, by Reed Garrett,a child that Claire had given birth to and put up for adoption beforeshe had met Mac. In season three Stella comes in contact with HIV positive blood. After waiting several months for the test results, Stella discovers she is HIV-negative using a viral PCR test administered by Adam Ross. The show used Stella's possible HIVinfection as part of a public service campaign on CBS. In Season 4,Stella bumps into a man named Drew during a case in Episode 2 ("TheDeep"). Drew seems to take a deep interest in her and keeps sendinggifts to her office. Drew is later revealed to be Mac's 333 caller. Inthe season 5 opener ("Veritas") she is seen chasing Joe and Joe laterpushes her over a rail and gets away, but she is apparently strongenough to pull herself back up.