In the series finale, Jason's surgery to get rid of Ian is about to begin, but years of taking his blackout drug render him immune to normal anesthesia. Under the influence of stronger medicine, Jason flashes back to his childhood—and Ian's origins. Meanwhile, Jordan and Lena take separate paths to uncover Jason's secret.
Jason has an MRI that reveals a brain tumor after collapsing in front of Dr. Young, but his plan with Ruben to get rid of Ian during the ensuing surgery hits a snag when Lena may be on to them—and Ian isn't too keen on the idea either.
A surgery goes past 8:25 pm due to complications, so Jason takes a chance on Ruben's new drug to keep Ian at bay. However, the effects don't last as long as they'd hoped, which turns out to be bad news for Lena and Olivia.
Ruben hires a gang to mug Ian to obtain a sample of his spinal fluid, which he believes can be used for a drug to eliminate him, but the plan hits a snag when Jason is blackmailed by the thugs to get rid of one of their rivals.
Jason's secret is in jeopardy after he receives an anonymous text message threatening to expose him. Meanwhile, Olivia takes Cole to a place that reminds him of his father; and Jordan learns more about Jason's past.
Ian has a new love interest whom he met in D.I.D. therapy, but Jason worries about her health, and when he tries to help her it might mean the end of Ian's romance. Meanwhile, Dr. Jordan tells Dr. Young that someone altered her daughter's chart; and Lena pursues a new relationship.
Jason makes a deal with Ian that he can see Olivia, but only on the condition that Ian pose as Jason at a formal affair to honor Dr. Young, though the evening is nearly ruined by Ian's behavior, which pushes Lena away and puts Young's daughter in danger. Later, Olivia meets Ian in a hotel room, but it's a rendezvous he may soon regret.
Ian breaks an important rule by beating up a man in a bar brawl, which puts Jason's medical skills to the test. Meanwhile, Jason tries to mend his relationship with Lena; and Olivia is unnerved by Ian's stalking.
Jason's attempt to control Ian's spending backfires when the doctor comes to in a random sports car tailed by a drug dealer. Meanwhile, a falling out between Jason and Lena prompts a late-night visit from Ian; Dr. Jordan tries to get to the bottom of Jason's behavior; and Olivia worries about her son's new imaginary friend.
Successful neurosurgeon Jason Cole struggles to keep a lid on his dangerous alternate personality, known as Ian Price, but in this drama's premiere finds he can no longer control his lethal side, who's grown immune to his oppressor's serum and can now run wild at the same time every night, threatening Jason's life and career, and everyone he knows.