The discovery of a badly decomposed body pits Mac and his team against an efficient killer using the parents of one of his victims to manipulate crime scenes. One of the victim's mothers received a voicemail message with directions on how to locate the body of their son, Jeremy Harris. The parents follow the detailed directions and in the process destroy physical evidence; which is the killer's intention. The body was not Jeremy but a second victim, Craig Anderson. Soon the mother receives another message and despite her husband's objections, follows the killer's demands and is almost killed in a fire before Jo saves her. Two key pieces of evidence at the scene, a bloody apron and snake skeletons, lead the team to the unsolved case of a bouncer shot at a local night club and killed. The girlfriend of the bouncer, Allison Scott, worked as a bartender at the club and was at the scene when her boyfriend was shot; his blood was on her apron. She blames the shooting on two men her boyfriend had a fight with that night, Jeremy Harris and Craig Anderson. Allison poisoned them with snake venom and watched them slowly die. She was recently arrested on drug charges and was afraid police would now match her prints to the crime scene so she paid a friend to make the calls to Jeremy's mother. Jo visits an unremorseful Allison is prison and gets Allison to tell her where Jeremy's body is. When Mac and the team arrive at the location they find Jeremy is still clinging to life. Jeremy survives and is reunited with his grateful parents. Jo's eleven year old son Ellie is having a hard time adjusting to life in New York City and this case definitely hits home for Jo, having two boys of her own.