Plot summary
The Machine orders Root on several tasks such as helping a convict escape and using him to impersonate a Department of Defense employee in order to obtain a secret note. Afterward, she and Harold's team coincidentally reach the same person, a janitor. It later turns out that NSA has been testing an advanced supercomputing chip and the janitor was one of the 15 people who had access to the development lab. This makes both Decima and Vigilance come after him. While Harold and his team's assignment was to protect the janitor, Root had to stop the chip from falling into Decima's hands. They are able to save the janitor, but Decima gets the chip.
Credits
Adapted from Wikipedia contributors, Person of Interest season 3. HTML formatting and reference markers removed.