Rigsby goes to a martial arts fight with a friend. While they watch the action in the ring, a gruesome murder takes place backstage. The victim turns out to be Charlotte Mitchell, an author who was writing a book about the fighters, Rowdy Merriman and Manny Flaco.
No one involved in the fight claims to know what happened. It's learned that the gun used to kill Charlotte was also used in a murder in 2001 committed by Joe Reyes.
Rigsby contacts Joe Reyes for questioning. Reyes, who found God while in prison, has become a preacher. He reports that he gave the gun to Dawn May, whom he hasn't seen since his arrest. Meanwhile, Lisbon and Jane contact Mitchell's dad and obtain her notes for the book she was working on. Charlotte's dad, Tom, suddenly has a heart attack during the interview and is sent to the hospital.
Next the team goes to the gym where Jane talks to Merriman's former trainer, Floyd Benton. Benton suggests Merriman isn't all what he seems to be. This resonates with Jane, who noted earlier Merriman's apparent disrespect for women.
The investigation hits a wall when Dawn May claims to have given the gun to her cousin Bobby who was killed in Iraq. Then new information emerges that Charlotte had arrived at the fight an hour before it started. As a result, both fighters are called in for questioning. Jane goads Merriman into revealing his lack of empathy for women as he hints that his opponent, Flaco, was having an affair with the writer.
This seems likely, given that Flaco's wife is bitterly decrying her husband's affairs in the next room. She also might have seen Charlotte talking to Floyd Benton. So, Benton is next to be called in for questioning. He denies any involvement with the murder and accusations that the fighters were using steroids or that there was some kind of fix put on the fight.
Jane begins scouring Charlotte's notes for clues, and Rigsby gets a visit from Joe Reyes, who admits that he lied about not seeing Dawn after he gave her the gun used in the murder. And Dawn also lied because she was afraid of getting involved. Turns out, Dawn gave the gun to a man named Frank Lopez. Lopez claims to have lost the gun in a fight at a nightclub club owned by Len Artash.
Jane and Lisbon head back to the gym to speak with Artash and Benton. Jane tricks them into thinking that the answers will eventually be found in Charlotte's notes once her father gets healthy enough to help decipher parts that are written in code.
All Jane and Lisbon have to do next is keep an eye on Tom's room in the ICU. Flaco's trainer, Suge Lima, shows up with his own pillow and attempts to smother Charlotte's dad with it. Unbeknownst to Lima, Tom has been moved from the ICU and replaced with a dummy. The incident leads to the arrest of Len Artash. Lima gave his own blood as sample so that Flaco's bloodwork would not show blood in hie cerbrospinal fluid, and thus ending his career. Artash and Benton conspired to murder Charlotte because she had found out about their illegal activities and threatened to tell on them.