Plot summary
During a mission to eliminate four suspected terrorists, ISA operatives (including Brooks and Grice from "Honor Among Thieves") eliminate three while the fourth, Yasin Said, escapes with his laptop. When Control requests access to the laptop's contents, Samaritan denies the request. Suspicious of Samaritan's actions, Control orders Brooks and Grice to make recovering the laptop their highest priority. But when they do so, Said escapes and the laptop self-destructs. Reese and Root, who have been hunting for Shaw, kidnaps Control. Root tortures Control for information on Shaw, but Control denies having any knowledge.
Harold realizes that Control herself has been kept out of Samaritan's plans. Harold uploads a worm to one of the cellphones of the ISA operatives who came to rescue Control. Control tracks Yasin to Canada. He reveals that he won the Nautilus puzzle (from "Nautilus") and he wrote some software for an anonymous corporation. Control kills Yasin, but her actions leave a hint of doubt in her mind. The young boy acting as Samaritan's representative approaches White House and demands for a meeting with the President. Control visits the site of the shootout between Harold's team and the Samaritan operatives at the New York Stock Exchange.
Credits
Adapted from Wikipedia contributors, Person of Interest season 4. HTML formatting and reference markers removed.