The crew try to rescue some scientists who have been working deep underground on a planet that has been taken over by militants; Dr Phlox meets resistance from a dying patient.
When pieces of a body are found in different rubbish dumps, the police find a suspect but struggle to work out a motive.
When a prominent atheist leader is kidnapped and murdered, detectives Goren and Eames interview the victim's granddaughter, who was also kidnapped.
Finn probes the mysterious suicide of a 12-year-old girl whose mother said the child was dying of cancer; Potter's friend is arrested for cocaine possession after a birthday party they both attended.
The death of a professional tennis player leads the task force to a doctor who may be fixing the odds for a major sports betting syndicate; Red digs deeper into Dembe's betrayal; Ressler struggles with sobriety.