Set in 1597, The Red Lion follows young criminals Kit Skevy and Mariner Elgin, who accidentally rob the wrong grave and find themselves entangled in the dangerous world of Tudor alchemy. Kit, a fearless brawler who feels no pain, is kidnapped by the ruthless alchemist Lord Isherwood and his son Lazarus, while Mariner, a skilled cutpurse disguised as a boy, seeks help from a rival alchemist, Lady Elody Blackwater. As they navigate the treacherous schemes of alchemists and gang lords, their friendship is tested, and their survival depends on outwitting those who would use them for their own dark ambitions.