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.

When 133 African prisoners are thrown overboard from a slave ship in suspicious circumstances, Garrow challenges the brutal trade that regards slaves as cargo. It is a case that amounts to a declaration of war.

Garrow defends a man accused of sodomy, a capital offence in Georgian England. But Garrow is embroiled in a simmering sexual scandal of his own - Sir Arthur Hill has accused him of adultery with his wife. In representing an accused homosexual, Garrow risks gossip and humiliation. And, it turns out, he must also perpetuate a lie.

Returning from war, weary and wounded, British sailors are treated with contempt and abuse at the Greenwich Hospital. One man bravely exposes the corruption, and finds himself in a Newgate cell. Southouse accuses Garrow of mixed motives as his uses the case to attack The Admiralty - and in particular its Under Secretary, Sir Arthur Hill.

William ends up risking his reputation as he returns to the Bailey to defend James Hadfield, who is on trial for high treason for trying to eliminate King George III. He continues to enjoy an "irregular" relationship with Lady Sarah Hill and finds himself ostracised and impoverished. Separated from her husband, Sarah learns from Southouse that she has no independent rights of her own.