Simon McBurney and Mickey Sumner also star in this portrait of a top surgeon under mounting pressure following a procedure marred by complications.

New Zealander Christine Jeffs, who turned heads with her homegrown 2001 debut Rain before segueing to U.S. projects with Sylvia and Sunshine Cleaning, returns to features after a 16-year break with A Mistake. Sensitively observed, measured and perhaps somber to a fault, the medical drama about accountability is most notable for Elizabeth Banks’ compelling lead performance as a distinguished surgeon facing the professional and personal consequences of a questionable decision in the operating theater.

Elizabeth Taylor (Banks) is a surgeon in an Auckland hospital, considered among the best in her field. During a laparoscopic procedure on Lisa (Acacia O’Connor), a young woman with advanced septicemia, Liz entrusts her student doctor, Richard (Richard Crouchley), to insert the last trocar to drain fluid. He misjudges the amount of pressure required, rupturing an intestinal artery and necessitating a more invasive surgical fix.

The scene gives us a succinct take on Liz as both a doctor and a nurturing leader of her small team, including Richard and scrub nurse Robin (Mickey Sumner), who is also her romantic partner. Liz is calm, self-possessed and good-humored, clearly practiced at keeping stress to a minimum in the operating theater, so when Richard starts freaking out over his error, she quickly talks him down and gives precise instructions as they deal with the emergency. Only once she steps away from the table and removes her gloves and mask do we see the strain on her face.

Jeffs punctuates the action with Liz’s ferry crossings between work and her house across the harbor. The wake churned up by the boat seems to suggest turbulence ahead. Sure enough, bad news comes via text during her commute the next morning, informing her that Lisa died during the night in Intensive Care.

Richard is highly agitated, but Liz insists that the patient probably wasn’t going to make it anyway: “All we can do now is move on. Get past it. Get better. Learn.” But moving on becomes more challenging when Lisa’s grieving parents (Rena Owen, Matthew Sunderland) ask to see Liz, wanting detailed answers about why their 29-year-old daughter died.

Banks gives a steely, largely internalized performance through the establishing scenes, gradually letting emotion creep in as Liz grows more isolated and even Robin pulls away to safeguard her job.

As the fallout from the patient’s death continues, Liz attends a surgical safety conference and is passionately outspoken about her objections to a new push for greater transparency from hospitals, with full results of surgeries to be made public. She argues that good doctors will start refusing to operate on the most vulnerable patients rather than risking their reputations and being hung out to dry by hospital administration: “People will be crucified.”

A tragedy hastens her unraveling even as it presents a damage-control opportunity to Andrew, played by McBurney as a chilly, mildly condescending man, more bureaucrat than medic at this stage in his career. “It’s called cleaning the wound, Elizabeth,” he tells her, while stressing that they need to agree on one version of what happened.