A body blows up the morgue, killing an attendent and destroying several other bodies. At first, the team thinks that the attack was related to a cartel hit, but they then realize that it was about an earlier murder and destroying that body to conceal evidence.
The first victim was a drug-dealing roller derby player, but it wasn't her boyfriend who did it because he had an alibi. Plus, he apparently had no motive. Sherlock discovers a small hidden camera in the woman's apartment, and they discover that one of her drug clients was spying on her.
The kid is revealed to be quite mentally disturbed and obsessed with her, and Sherlock locates a cache of mutilated photos in his bedroom. However, they later realize that the teen's father killed her, and then set the bomb to destroy the evidence.
Meanwhile, Detective Cortes contacts Joan and tries to enlist her help on a case. Sherlock warns Joan that Cortes is probably playing games, and Joan realizes this is true. Cortes does reveal that she is committing vigilante attacks on criminals and attempts to enlist Joan in her activities.
Joan declines and warns her not to continue with her violent activities, or else Joan would prove that it was Cortes doing them.