Dr. Jason Cole wakes up and checks his bedside table to find an empty medicine cartridge, the remnants of another safe night's sleep. Jason is an accomplished and well-respected surgeon. Before scrubbing in for surgery at the hospital, he puts his watch down on the counter. It's counting down to 8:25 p.m. The hospital requires that Jason perform a glucose test before beginning surgery, to be sure that his blood-sugar levels are normal.
Next, Jason meets with his friend, Dr. Marcado, a hospital chemist who secretly provides him with a powerful, custom-made sleeping elixir. Dr. Lena Solis catches Jason in the hallway and invites him out for drinks. Unfortunately, Jason must decline. It's imperative that he gets home before 8:25pm. After work, Jason heads to the local church for a dissociative identity disorder support group meeting.
During the private meeting with his sponsor, Will, Jason explains that he suffers from a multiple personality disorder. His alternate personality, Ian Price, shows up every night at 8:25 and wrecks havoc on Jason's life. As a result, Jason has gotten into the habit of drugging himself into an incredibly deep sleep every night to keep Ian at bay. So far, it seems to be working.
Will suggests that Jason surprise himself a little, so Jason heads to a bar to meet Dr. Solis for drinks in his last few minutes before 8:25. At the bar, Jason and Lena hit it off. They clearly have chemistry, but Jason must cut the date short. He must get home before 8:25. Jason rushes home and injects himself with a powerful sedative in the nick of time... or so he thinks. The sedative doesn't work, and Jason is powerless as Ian takes over.
Jason wakes up the following morning surrounded by half-naked escorts. He is in a swanky penthouse apartment. The place is a wreck. Blurry memories of the night's crazy party slowly come back to Jason. Ian has been here, and he's been up to no good.
Jason rushes into work and orders his assistant to set up a series of tests and exams for him. He cancels all of his appointments and asks his colleague, Dr. Jordan, to cover his rounds. Jason meets with a patient who is suffering from a tennis-related elbow injury and later apologizes to Lena for leaving the bar so abruptly. Lena wants to help, but Jason can't let her in.
Jason meets with Dr. Marcado again to ask him why the elixir isn't working anymore. Dr. Marcado promises Jason he'll get to work on a new formula. In the meantime, Jason needs to figure out how to keep Ian at bay tonight. He catches a cab to a seedy motel on the outskirts of town. In his last moment before Ian takes over, Jason scrawls on the foggy mirror: "Do No Harm." Ian takes over and promptly wipes the message out.
Meanwhile, back at the hospital, one of Jason's patients wakes up in the middle of the night to head to the restroom. He catches a glimpse of himself in a mirror and is horrified by what he sees: his face in his reflection appears horribly disfigured. Unable to control himself, he begins screaming and panicking. A team of nurses rushes in to sedate the patient.
At the hotel, Ian surveys his surroundings. He searches for Jason's personal belongings, but finds that Jason has hidden his money and credit cards. The only thing Ian finds is a slip of paper with Lena's phone number on it. He calls the number and invites Lena to meet him at the hotel. When Lena arrives (thinking that Ian is Jason), Ian forces himself upon her.
Jason wakes up coughing at 8:25 the following morning. He immediately realizes that Ian has been playing all night. Jason heads to the hospital and asks his assistant to cancel his cell phone, his credit cards and anything else that Ian may have sabotaged last night.
Jason's first task of the day is to meet with his patients, including the patient who suffered a traumatic episode the night before. He explains to his patient that he suffers from prosopagnosia, a neurological disorder that prevents him from recognizing faces. While performing the surgery on his tennis-injured patient, Jason discovers that his patient's injury isn't tennis related at all. She's being abused at home.
After his surgery, Jason runs into Lena, who seems terrified of him. Jason realizes that Lena encountered Ian last night, and that the resulting encounter was less than appealing to Lena. Jason tries to explain, but Lena won't hear it. Jason heads to his office and calls his old girlfriend, Olivia, to inform her that Ian has been released.
Jason takes a train to meet Olivia, with whom he shares a long and sordid history. Once Jason proves that Olivia is talking to him and not Ian, he informs Olivia that Ian will be coming for her. He advises Olivia to get as far away from him as possible.
Back at the hospital, Jason meets with his tennis-injured patient. He informs her that he knows someone is abusing her, and that it would be in her best interest to stop protecting him. The patient tells Jason that her husband is the one abusing her, but she can't turn him in. Jason vows to help his patient in any way he can.
Jason meets with Dr. Marcado, who suggests that Jason lock himself in a psych ward cell for the night to keep Ian from destroying anything, but Jason has another idea. He's going to use Ian to his advantage. He heads to the home of his abused patient to let Ian confront her abusive husband. Ian takes over in the nick of time and engages in a brutal fistfight with the wife-beater, who eventually promises to never hit his wife again.
After the fight, Jason is paged to the hospital for emergency surgery. Ian decides to fill in for this one. Before performing the surgery, Ian must clear the glucose test. He fails the test, and the other nurses tackle Ian to prevent him from going into a diabetic shock. Ian is rendered unconscious, and Jason wakes up in a hospital bed the following morning.
Jason explains to Dr. Marcado that it was his plan to have Ian attempt the surgery. He knew that Ian's adrenaline would trip the glucose machine and that the nurses would knock him out for the remainder of the night. Jason heads straight to the operating room to perform a risky brain surgery. Meanwhile, Dr. Jordan begins investigating Jason's past.
Jason checks on his patients, who are all better off thanks to him. On the way out of the hospital, he catches Lena and asks her to explain what happened the night she met Ian. As much as he apologizes, Lena is not convinced. Jason tells Dr. Marcado that he wants to eliminate Ian altogether and Dr. Marcado reluctantly agrees to keep working on a cure.
Jason records a video for Ian, offering to leave Ian alone if he agrees to stay out of Jason's life. Ian doesn't approve of the conditions. He immediately heads to Olivia's house, where he encounters Olivia's son, Cole. Whatever Ian has planned for Olivia and Cole, it's not going to be pretty.