When Erin tries to take down a gang leader using his law-abiding brother as bait, the family debates her methods.

The Reagans argue the advantages and disadvantages of profiling; Danny, Frank and the rest of the NYPD search for a homemade bomb about to detonate.

A good Samaritan with a police record takes action against a terrorizing subway criminal, forcing the Reagans to weigh the rights and wrongs of vigilantism.