The first response paramedic team gets ready for the day. Nancy Carnahan gives her new love interests and partner, Terry Banner, a tell-tale smile. Cameron Boone and Tyler Briggs know Nancy and Terry are in a relationship. In the ambulance, Nancy tells Terry that she doesn't care if Tyler and Boone know.
As the work day comes to an end, James Walker, an electrician, stays behind to fix a roof transformer. A coworker, Thomas Fitch, is unaware of Walker's position and turns on the main power line, which sends 30,000 volts of electricity through Walker's body. Emergency services are quickly notified and paramedics Tyler and Boone are the first to get the call. Boone talks to Fitch on the phone to keep Walker alive. Back at San Francisco City Hospital, Dr. Saviano preps his interns for the incoming victim. Meanwhile, Nancy and Terry are getting hot and heavy in the ambulance when the emergency call comes in.
Boone and his partner, Tyler, are first on the scene and immediately start CPR on Walker. Nancy and Terry quickly assist. Flight medic Reuben "Rabbit" Palchuk checks on the team and Walker starts to flat line. Rabbit calls Walker's wife to let her know that Walker has been in an accident. During the conversation Rabbit learns that Walker has been in the military and has been on anxiety medication. This means Walker is immune to adrenaline, and is not responding to the paramedics' efforts. As soon as Nancy gets a pulse, Rabbit takes Terry in the helicopter to bring Walker to the hospital.
En route to the hospital, a news chopper collides with the medical chopper and crashes into the building. Nancy, Boone, and Tyler are left in horror on the roof as the debris from the accident flies over their heads.
It is exactly one year after the infamous accident that took seven lives, including paramedic Terry Banner's. The surviving paramedics try to get on with their work. Boone sits with his family for breakfast, but his wife Sela wants to know why he came home at four in the morning. On a different side of town, new pilot and Iraqi veteran, Marisa Benez, tries to ease her mother's concerns. At work, Nancy and Boone discuss a co-worker's return. Boone asks Nancy why she even came today and Nancy responds, "Because I need a save today."
Nancy and her new partner, Bailey, rush an injured man to the hospital. Nancy tells the intern not to sedate him because he's too drunk. At the hospital, Dr. Saviano tries to convince Nancy to join a residency program, but Nancy declines, saying that medical school just wasn't for her. Saviano tells Nancy that Rabbit will be coming back to the team. Nancy doesn't want to deal. Marisa gears up for her first day on the job and meets her partner, Rabbit. Marisa and Rabbit are off to a rough start when Rabbit tells her it's "his copter, his world."
A negligent driver, Bobby Newton, is texting on his Blackberry on the way to a meeting. The texting driver cuts in front of an 18 wheeler and causes a huge collision on the freeway. Dr. Saviano prepares his team for the accident victims. Marisa and Rabbit take flight and Boone and Tyler are the first on the scene and tend to Newton.
Boone realizes the oil tanker is leaking and gets as many people out of the way as possible before the huge explosion. Once the explosion happens, a piece of metal from a car pierces through the windshield of the carpool mother's car and penetrates the neck of her 10-year-old son, Sammy.
Nancy tries to save a John Doe who seems to have walked right into the accident. Rabbit tends to Newton and sedates him so Tyler can work in peace. Boone rushes to Sammy's aide and calls Rabbit to his side. Rabbit sees the boy needs immediate attention and rushes him to the helicopter. Nancy continues to do CPR on the John Doe and pumps him full of medicine to try to bring the victim back to life. The John Doe wakes for a moment and then flat lines again.
In the helicopter, Rabbit, despite Dr. Saviano's opposition, decides to do a tracheotomy to save Sammy's life. Sammy's mother must help to ensure her son doesn't bleed to death. Rabbit sticks a tube down the hole in Sammy's throat and the boy begins to cough and breathe again. The grateful mother cries tears of joy. Nancy and Boone still work on the John Doe, but Boone is trying to convince Nancy to stop. The John Doe is not coming back to life. Nancy yells and screams to get John Doe back alive. Finally Nancy listens to Boone and stops. Nancy walks away from the man, disheartened and beaten down.
At the hospital, Dr. Saviano's team picks up Sammy from the helicopter. Down on the freeway, Tyler puts a toe tag on the John Doe. Boone sees an attractive young woman named Leggy, who has a broken arm. He escorts her to the helicopter. However, this is not protocol for a broken wrist. Rabbit approaches Nancy, who is looking out over the bridge. Nancy wants to be alone and Rabbit wants to know why she let the John Doe get to her. Nancy feels alone, just like that John Doe. Rabbit tries to console her by apologizing for Terry's death a year ago in the helicopter accident.
It is the end of the day and the paramedics unwind near the Golden Gate Bridge. Rabbit confronts Boone about taking Leggy in the helicopter. He scolds Boone for using the helicopter for trying to get a woman. Boone tells Rabbit that after the accident, no one knew if Rabbit was still alive and everything felt pretty much over. He confesses to Rabbit that the night of the wreck was the first time he didn't come home. Boone wants to protect Sela and the girls from the everyday horror paramedics go through. Rabbit says that he will be there for Boone at any time.
Later that night, Rabbit and Marisa get to know each other. Rabbit gives Marisa a ride and tells he that he can't die, as he drives recklessly through the streets of San Francisco. Marisa starts to get mad and worried when Rabbit doesn't stop. But Rabbit has survived "hell and fire" and all odds say Rabbit should be dead. Marisa tells him he needs to stop being reckless and right then, Rabbit crashes into a parked car.
The driver of the parked car is drunk and takes responsibility for Rabbit's accident. The drunk driver goes to wander off home, but Rabbit stops him and notices that the man is missing a finger. Rabbit runs and gets ice so they can sew the finger back on. After Rabbit sees the driver into an ambulance, Marisa slaps Rabbit for being an irresponsible idiot. She is angry at Rabbit for putting her life in danger and tells him to "pull back on the craziness" and get his act together.
At the hospital, Nancy tries to check on her John Doe to see if anyone has claimed him. Dr. Saviano comes to sit with Nancy, seeing that she is obviously sad and shaken from the day's events. Saviano tries to console Nancy about the wreck that happened a year ago and the loss of her friend, Terry. Upset and lost, Nancy looks in at the dead body of the John Doe and cries; feeling that they have more in common than they should.
The night comes to an end and Boone takes the tram home to find his sleeping children in their beds. He kisses each of them lovingly. Marisa calls her mother to ease her concerns of the day. Rabbit, at his apartment, gets a surprise visit from Nancy. Nancy claims she can't sleep and Rabbit says that he too is having trouble sleeping. As dawn breaks, Rabbit and Nancy lie in bed together. Nancy caresses Rabbit's scar from the accident and welcomes him back.