Nambi E. Kelley

Flashbacks to Finch's adolescence provide insight into his creation of The Machine. Also, the team receives the number of an already dying man, and Reese leaves the POI team behind in the aftermath of the war with the crime organization, HR. Camryn Manheim and Saul Rubinek guest star.

Elizabeth makes a secret trip to Iran in hope of preventing a coup that could affect President Dalton's administration; Elizabeth's staff is brought up to speed on the investigation into Marsh's death.

Sherlock is forced to work with his estranged brother, Mycroft, in order to solve a case that has life-or-death consequences.