Margaret did an open cholecystectomy on John Terzian. Five days later, he came back to the ER after falling down the stairs when his incision hadn't healed as quickly as he wanted. A CT revealed that Campbell had nicked the bile duct. Despite this mistake, John asked that Campbell do the repair herself.
In surgery, she quizzed Cristina, who believed she was a dinosaur who had no business operating anymore. When Cristina offended her, Campbell kicked her out of the OR. After the surgery, Owen talked to her about being discharged from the Army, saying the Army knew it was his time even though he didn't.
She later said she had decided that John's surgery would be her last.
Margaret and Cristina Yang have a mutual dislike for each other.
Dr. Campbell was Seattle Grace's first female surgeon and the surgical generation above that of Richard Webber and Ellis Grey. Callie describes her job as "mostly she just sits around in her office and spreads prestige around, but she still does routine surgery now and again." She identifies herself as a God with a scalpel.
It was hinted that she taught Richard Webber and it has been years since he's been in her OR, and does not let him forget the time he dropped a clamp into an open body cavity. She worked with Ellis Grey, as is documented in her journal, March 3rd 1979, where Ellis assisted her on a splenectomy (surgical removal of a spleen), and is described as "impressive résumé, adequate technique".
Cristina calls her "a dinosaur that refuses to retire her scalpel" after she does not use laparoscopic methods for a cholecystectomy on her patient, John Terzian, who developed a post-operative infection, severe enough that Callie believe the infection is the reason Mr. Terzian collapsed. On a the CT scan, Cristina and Owen find a lacerated bowel duct and artery from her surgery; a mistake that should not have been made, open surgery or not.
As one of the most senior surgical attendings at Seattle Grace, she outranks Owen Hunt and he is forced to defend her choice of open surgery instead of minimally invasive surgery when explaining the problem to the patient, in contrast to Cristina's criticism of Dr. Campbell's choice of procedure.
During surgery, she teaches Cristina, after criticizing the new teaching methods of inspiration, using the her methods of fear and shame she was taught with, asking Cristina how to perform a pulmonary embolectomy (removing a clot in the pulmonary vessels). Cristina correctly and accurately describes the procedure using "newer" methods (inserting a steel wire catheter into the femoral vein and removing the clot using a fluoroscope for guidance by placing the scope adjacent to the embolism), to which Dr. Campbell retorts with a power failure, or a hospital without a fluoroscope, leaving Yang speechless, and Dr. Campbell makes her point using an analogy of teaching mental arithmetic to young children and the use of calculators. Cristina fights back by with "If it will help them to to avoid mistakes like this one", infuriating Dr. Campbell and being kicked out of the OR.
Following the surgery to repair her original botched procedure, Owen confides that he was discharged from the army because they knew it was his time, and this prompts Dr. Campbell to retire because Richard is reluctant to fire her. And it is while she decides to retire is when Yang finally has an answer for her, using old-fashioned manual removal methods to remove an embolus. Dr. Campbell commends her, for finding her and for giving the correct answer, leading her to conclude she will be a much better surgeon than she initially thought, pleasing Cristina.