Person of Interest shook up its team in a big way when it added Sameen Shaw to the fold in season 3. Played by Sarah Shahi, Sameen Shaw joined the CBS series in a recurring capacity in season 2 before being made a permanent member of the team in the beginning of the show’s third season. The addition of a new special agent into the mix changed the dynamic of the show, no doubt leading some viewers to question why the writers would gamble with a proven formula.
In a season 2 episode, Reese (Jim Caviezel) met Shaw, a special agent for the government whose job was to stop terrorist threats. It turned out that Shaw and her partner’s work for the government was related to the Machine. Her objectives came from the “relevant” numbers provided by Finch’s Machine. After she and her partner learned more than they were supposed to know about their missions, her partner was killed and Shaw was forced to go on the run. It was during this time that she first teamed up with Reese. Though they parted ways, Shaw returned near the end of the season and helped the team find Root (Amy Acker). Starting in season 3, Shaw was made a full member and was told the truth about the Machine.
For the first two seasons, Person of Interest centered on the duo of John Reese and Harold Finch (Michael Emerson). They had allies in Lionel Fusco (Kevin Chapman) and Joss Carter (Taraji P. Henson), but these were characters who mostly provided intel and occasional support through their connections in the police force. In season 3, Shaw became the first character to become a full-time addition. According to Person of Interest creator, part of the reason for Shaw being on the team is her “connection to the relevant world” [via TV Goodness].
A big part of Person of Interest was this idea that the crimes predicted by the Machine were divided into two categories: “relevant” and “irrelevant” numbers. Both were discussed often, with irrelevant numbers being the focus of Reese and Finch’s mission on the show, but it wasn’t until Shaw joined the series that viewers got a glimpse into the other side of the Machine. Through Shaw, much was learned about how the government made use of Finch’s creation.
Nolan says that she also served the purpose of being a “foil” to Reese. What concerned some fans about Shaw joining the team was that she was too similar to Reese, and to some degree, this was true. With her experience, she was sometimes seen as an equal to Reese in terms of what she brought to the table. Both were incredibly skilled with guns and in hand-to-hand combat. There wasn’t much that Reese could do that Shaw couldn’t. But personality-wise, she contrasted with him in an interesting way. Their different perspectives and approaches to their work gave them a dynamic that worked well for the series. Shaw’s presence also had other advantages later on down the line, as Person of Interest slowly built up to a romantic relationship between her and Root, and also gave her plenty of fun banter with characters like Fusco and Finch.