Irritable and irascible, Dr. Mark Craig was the hospital's lone superstar. An arrogant but brilliant heart surgeon who could easily have left the halls of St. Eligius to take a position at rival Boston General, he chose not to and stayed on to act as mentor and tormentor to the hospital's young doctors, especially to protege Dr. Victor Ehrlich. Dr. Craig would not hesitate to toss a bullying and sarcastic barb at any doctor, nurse, administrator or patient who happened to pass his way. During one story arc, Dr. Craig develops an artificial heart (the "Craig 9000"), which he eventually tests on a human subject; the failure of the heart brings a fleeting moment of self-reflection to the otherwise supremely confident doctor. In one of St Elsewhere's most-compelling moments, Dr. Craig witnessed the autopsy of his only son, from whom he had been estranged due to his own autocratic ways and his son's drug problem.