In Who is Erin Carter?, DI Jim Armstrong is an officer of CIO, Centralized Intelligence and Operations, who hires and trains Erin for a job that changes her life forever. Jamie Bamber plays Jim Armstrong.
Jim Armstrong approaches Erin Carter when she gets kicked out of the police academy for hurting a bully. Jim claims that Erin was never going to make it as a cop. However, Jim sees her potential and invites her to join CIO.
CIO is known for running covert law enforcement units. They infiltrate extremist groups and criminal organizations. Erin is not a police officer, but she makes a great criminal. She is trouble, but Jim finds use for trouble, so he hires her.
Jim trains and prepares her. While working for him and CIO, Erin attempts to infiltrate Thomas Ramsey’s gang, which is looking for a driver.
At first, when Margot, a member of Ramsey’s gang, doesn’t respond after interviewing Erin, Jim wonders if he put her out before she was ready.
Erin proves how good she is by putting on an act where she flirts with Jim. Moments after that, she receives a call from Margot, and she joins Ramsey’s gang.
Why does Erin betray Jim?
The next time Erin and Jim meet, Jim realizes that Erin has gotten too close to Lena, a member of Ramsey’s gang, who has a daughter named Harper.
Jim asks her to stay focused and even assures her that he will pull her out immediately if something goes wrong. He even promises her a future at CIO.
Erin figures out that it’s a fake promise when she calls Jim after almost getting caught. Ramsey’s gang killed a member of theirs, suspecting that he is a mole working for the police.
Erin tells Jim about this, but Jim’s seniors want Ramsey’s heist to play out. Ramsey’s gang carries out the heist, and a war between the gang and the cops begins.
Erin barely survives the war and rescues Harper after watching Harper’s mother get shot. Erin now knows she was always disposable to Jim and CIO, so she decides not to return to them. With some of the stolen bullion in her hands, she leaves to restart her life with Harper.
In the finale of Who is Erin Carter?, after taking care of Daniel Lang, Erin goes on a vacation with her family, where she crosses paths with Jim again.
Jim assures her that he isn’t going to arrest her on her holiday, but he reminds her that holidays always end. Jim says she is trouble, and he has always found a use for trouble before letting Erin walk.