In the late 18th century, young idealistic barrister William Garrow is given his first criminal defence case at the Old Bailey by attorney and mentor John Southouse. He defends Peter Pace, who is accused by renowned thief-taker Edward Forrester of robbing a man at gunpoint.

The case is won by Garrow's nemesis Silvester, but Garrow's impressive performance in court catches the eye of Lady Sarah Hill. She instructs him to defend a helpless serving girl, Elizabeth Jarvis, who stands accused of murdering her newborn baby.

Garrow learns a harsh lesson from his first case, and vows to defend the life of Elizabeth.

William Garrow is now a celebrated Old Bailey barrister and, encouraged by Southouse, he defends the case of the infamous Monster, a man who carries out a series of stabbings on young ladies across London. As a result, Garrow's popularity diminishes with the public and the press. However, Renwick Williams, the accused, is described by Garrow as a 'lecherous libertine' and his defence is not easy. Garrow's friendship with Lady Sarah grows closer, a fact which does not go unnoticed by her husband, Sir Arthur.