Jack Shephard is a spinal surgeon at St. Sebastien Hospital in Los Angeles. He was aboard Oceanic Flight 815 because he was bringing the body of his deceased father Christian back from Sydney. Jack was previously married to a woman named Sarah, who was severely injured in a car crash. Despite his serious doubts that his could successfully operate on her spine and avoid paralysis, the surgery worked and they fell in love and got married. The marriage soon fell apart, however, and Jack was unmarried by the time he boarded the fateful flight.Jack had a tumultuous relationship with his father, who was an alcoholic and also the chief of surgery at the hospital where Jack worked. Jack effectively ended his father's medical career by revealing that Christian was drunk during an operation in which his patient died. Christian told Jack from a young age that he didn't have to be a hero and try to save other people, but Sarah told Jack as she was leaving him that he would always need something to fix. She leaves after revealing that she's been cheating on him -- an admission that came only after Jack told her that he'd kissed the wife of a patient who died after surgery.The series opens with Jack's eye opening on the island after the crash, and he quickly becomes a leader among the survivors of the plane crash. He forms a bond with Kate Austen. This creates a rivalry with Sawyer, who is also attracted to Kate. She seems to enjoy the attention she gets from both men and is in no rush to formally choose one over the other. Jack is often called upon to address the medical needs of the crash survivors, but also takes charge in collecting weapons, including guns and dynamite, and storing them for future use -- keeping them locked due to not fully trusting others to know about or have access to them.Jack seems to want nothing more than to get off the island, and to be the one who secures a safe exit for the group.