Folsom, Serena, and Jack check out a skeleton found in the wilderness. The skeleton held an additional skull. Folsom estimates the victim, Harrison Cantwell, has been missing 40 to 50 days. At another crime scene, a homeowner, Molly Tate, shoots an armed assailant. Max notices that Molly had received electroshock therapy. Max finds a card reading "Keep Your Secrets. Cull the Rotten Fruit" in the assailant's car trunk. Allie suggests that the skull and murder weapon at the first scene date back to the Ice Age. Cantwell was an amateur archaeologist. HIs associates identify his find as potentially a Clovis skull. The mentally ill Molly refuses to believe she was targeted and won't cooperate with Max. Folsom and Serena use a rubber ducky to determine how far Cantwell floated. Folsom hopes the tracker found on a dead coyote with Cantwell's foot in its mouth will lead to the murder scene. Beau identifies the substance Allie found in Cantwell's ear as granite. Folsom uses the tracker data from the coyote and looks for a site that includes granite and a particular cactus. Folsom and Allie find Cantwell's dig site, where he was killed. Cantwell's last call was to Dr. Qadiri. Max convinces Molly to give her the dossier that she had been sent. Cantwell's widow sent his notes to Qadiri. They both admit that they had been working together to improve Cantwell's chances at publication. They were together on a business trip when Cantwell was killed. Bloodwork reveals that the man who is Cantwell's killer has a particular condition. Museum director McArthur took Cantwell's last phone call. He has the condition they'd uncovered. He breaks down and admits to accidentally killing Cantwell. Serena tells Max that the skull reminded her of a case from her Miami days. Auerbach was Molly's therapist.