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.

After more derision from Silvester, Garrow is spurred on to defend Edgar Cole, a man who is accused of raping a servant girl. Garrow controversially wins and the detestable Edgar Cole is acquitted, much to the disappointment of Lady Sarah. She confronts Garrow but Silvester interrupts and senses the intimacy between them. His insinuation offends Garrow and he challenges Silvester to a duel to defend Lady Sarah's honour.

Garrow's next case sees him up against his old nemesis, the violent and unscrupulous thief-taker Edward Forrester. Forrester orders petty criminals Tom and Phebe to steal a box of lace from a shop owned by Katharine Stanton. Garrow seeks help from Southouse, but will his close friendship with Lady Sarah cost him his association with his dear mentor?