Joan discovers an unsolved murder connected to a rare prehistoric fossil when she reviews one of Sherlock's cold cases; Sherlock's responsibilities as a sobriety sponsor cross personal boundaries.
When a janitor violently attacks a coach, the SVU team connects the janitor's behavior to a history of sexual abuse; the detectives find more victims of the same predator -- including a prisoner (Mike Tyson) on death row.
A Russian nuclear submarine disappears in American waters, putting Elizabeth in a tricky situation; Stevie ends things with her boyfriend.
Danny forces his brother-in-law to help Baez take down the mobsters he's mixed up with; Frank suspects his old partner is guilty of a crime; Jamie is approached by an officer who wants help getting reassigned from his undercover assignment.
McGarrett's mom pays him an unexpected visit while the team investigates a polo player's death.