In BBC One thriller Trust Me, Whittaker plays Cath Hardacre, a nurse who loses her job after she turns whistle-blower.
Wanting to provide a better life for her young daughter, she steals her best friend's identity as a senior doctor and lands a job in an Edinburgh hospital (a colleague amusingly describes the A&E department as "like Braveheart with bad-tempered pensioners".)
Armed with her nursing knowledge and some medical textbooks, Cath sets out to bluff her way as an experienced emergency medic.
Of course, it doesn't all go smoothly. Trust Me contains several squirm-inducing scenes of medical procedures that don't go by the book
An early encounter sees her straighten a man's broken foot having forgotten to give him an anaesthetic. Imagine the screams.
Then there's a heart-stopping - and heart-breaking - sequence involving the victims of a car crash.
"There was blood squirting everywhere," says Whittaker, at a press screening that was held before the recent announcement she was to replace Peter Capaldi in Doctor Who.