The novel follows Pinkie Brown, a young gang leader in the English seaside town of Brighton. The novel opens with journalist Fred Hale being pursued by Pinkie's gang after writing an article that contributed to the death of their former leader, Kite. Pinkie's gang murders Hale, but Ida Arnold, a curious woman who had briefly met Hale, becomes determined to investigate the circumstances of his death.
Pinkie begins a relationship with Rose, a naive waitress, to prevent her from talking to the police after she finds evidence linking his gang to Hale's murder. Although he is Catholic, Pinkie is morally corrupt and plans to marry the underage Rose to keep her silent, even considering killing her through a staged suicide pact.
As Ida's investigation closes in on Pinkie, he grows increasingly desperate, murdering another member of his gang and attempting to flee with Rose. At the climax, Ida and the police confront Pinkie on a cliff, where he blinds himself with vitriol and falls to his death, unable to escape his guilt.