"Mea Culpa" is the 790th episode of Casualty and the ninth episode of the 26th series. It was preceded by "Charlie's Angels" and followed by "Sanctuary". The episode was directed by Tim Leandro and written by Stephen McAteer, and sees the arrival of doctor Sam Nicholls, portrayed by Charlotte Salt.
Fast-living, fearless and feisty, Major Sam Nicholls marches into the ED for her new job on secondment. So keen is she to get going that she turns up a day early asking to join a paramedic crew and get a feel for Holby. But Sam soon has to rely on all her army training when an aggressive driver with a grudge rams the ambulance crash at hospital heliport trying to get at the patient inside.
Meanwhile, Noel is keen to step up his security after a run-in with an angry patient. But a sensitive encounter with grieving mother Seonaidh convinces him that he doesn't want to be shielded from the public after all.