Plot summary
The Machine yields five numbers belonging to the respective heads of New York's major Italian crime families. Reese and Finch suspect Elias is planning to eliminate his competition, and Carter has the dons placed in protective custody. One of the dons is killed in a car explosion while another is killed in witness protection. Carter takes the remaining dons to a safe house, but is tracked down by HR cops. Elias has Carter's son kidnapped to force her to turn the dons over to him; Reese rescues Carter's son alongside Elias' father Gianni Moretti, against whom Elias wants revenge for ordering the murder of his mother Marlene.
HR cuts ties with Elias after Finch shows Simmons that Elias is targeting his and other corrupt officers' families. After Fusco calls for backup from honest cops, Elias surrenders to Carter and is finally arrested for his crimes. On his way to his prison cell, Elias places a call to his father and half-brother before having the two killed in a car bomb executed by his lieutenant Scarface.
Credits
Adapted from Wikipedia contributors, Person of Interest season 1. HTML formatting and reference markers removed.