UFC fighter Tito Ortiz will guest star in Numb3rs Friday, Feb. 16 (10:00-11:00 PM, ET/PT) on CBS. In the episode, Don (Rob Morrow) and the FBI investigate the mysterious death of a mixed-martial arts fighter after he dies in the ring while training for a championship match with his sparring partner.

David's (Alimi Ballard) friend becomes the main suspect after the FBI learns that the victim was poisoned, and another fighter who sparred with him also died in the ring while training. David tries to find evidence to clear the fighter even though they believe that he might have been knock...