The District Attorney’s Office is set on its ear when the investigation into the death of an A.D.A. uncovers a scandal that could imperil hundreds of cases.

The murder of a janitor in a university laboratory building leads back to a student employee whose participation in a drug study may have prompted the crime.

Cerreta and Stone find themselves on opposite sides of the fence when a storeowner kills two robbers and then claims self-defense as a justification.

Cragen comes under suspicion when his mentor in the department is investigated for laundering drug money.