S6·E6 Frail Mortality

The heads teacher's daughter who has been working as a house keeper for a sick man and his son, is knocked down in a hit and run accident. Maggie calls for help, but ends up becoming the main suspect. Obviously its not her, and Nick says he never suspected her, but Maggie's not so sure. The sick man can't remember anything of the night it happened because he blacked out, and is worried that he could have been responsible. But it turns out it was his son, who drove after the girl when she left that night (he had been her boyfriend) but panicked when he hit her. Nick reconsiders what Jo has said about promotion and asks Blaketon's advice about taking his sergeants exams.