Frank works to vindicate Detective Douglas McKenzie (Mike Carlsen), a detective accused of using excessive force. Also, Danny and Baez track down the killer responsible for the death of a rapper's bodyguard; Jamie is skeptical about a relationship between Espinoza (Luis Antonio Ramos) and a new rookie officer, Sarah Brooks (Lily Brown); and Eddie goes undercover to help Erin investigate a mysterious cult, on BLUE BLOODS, Friday, Oct. 25 (10:00-11:00 PM, ET/PT) on the CBS Television Network