Heartland introduces us to Dr. Nathaniel Grant (Treat Williams) an intense and overworked lung and heart transplant surgeon at St. Jude Regional Transplant Center in Pittsburgh. Grant is forced to deal with working in the same hospital with his ex-wife Kate (Kari Matchett), who is the organ recovery coordinator. The two must put aside their past differences and battle the clock in order to save lives.
Dr. Grant is now the chief of staff of the St. Jude Regional Transplant Center due to his friend and mentor Bart Jacobs retirement because of poor health. Meanwhile as Kate waits for clearance to remove the organs of a "Jane Doe" murder victim, she spends the day with her daughter Thea who is nervous about an upcoming party. Dr. Grant refuses to perform a living donation for a son who wants to give part of his liver to his dying alcoholic father. The episode also introduces us to Dr. Tom Jonas, who joins St Jude taking Grant's old position.
Dr. Griffith makes a bad incision during a liver transplant causing massive bleeding and forcing the liver to be discarded. The patient still has a chance for survival due to a possible living donation of the patients brother who is in prison for the murder of their foster father. Meanwhile Nathaniel treats a 13-year-old heart transplant patient who constantly comes back to the hospital with complications.
Tom is preparing to perform the first ever fetal uterine transplant on an infertile woman. However, he must get Nathaniel's approval before performing this breakthrough operation. Meanwhile, Nathaniel is preoccupied with saving the life of a six month old baby dying of a rare heart defect. Kate struggles to convince a grieving mother to donate her baby's heart, which could potentially save Nathaniel's dying baby.
Kate and Dr. Jonas travel to West Virginia to obtain the liver from a dying woman. However, Jonas encounters racism during their trip, which delays the organ recovery. Dr. Grant faces ethical issues when he meets a patient who is experiencing complications after receiving a liver on the black market in Mexico. Kate starts dating again.
Dr. Grant and his team perform an extremely complicated transplant procedure involving three married couples. Mary decides to make a personal sacrifice to insure the operation is a success. Meanwhile, Dr. Jonas' wife arrives and Bart's condition takes a turn for the worse leading his wife and Dr. Grant to push harder for him to get his much needed lung transplant.
A hostage crisis occurs at a local video arcade, which results in injuries and a possible organ donor from the perpetrator. However, the parents of one of the injured strongly object to his organs being used. Meanwhile, Kate trains a new organ recovery coordinator. Thea seeks to gain more independence from her parents.
Bart's health starts to decline to a critical state. Meanwhile, Dr. Grant and Kate travel to Cincinnati to recover a lung, which temporarily puts Dr. Jonas in charge of the hospital. Dr. Jonas immediately begins preparations for a complicated transplant procedure, which Grant initially rejected. Dr. Griffith makes a desperate attempt to impress staff due to the impending end of his fellowship.
In Heartland's dramatic season finale, Bart passes away and his widow would like Nathaniel to give the eulogy at his funeral. Meanwhile, panic ensues when it's discovered a former donor had cancer and it has been passed to the recipients of her organs. Kate feels responsible for the disaster and scrambles to find replacement organs. Dr. Jonas uses the opportunity to tell Kate how he really feels about her.