Basil, son of a father who values the family pedigree and who would not let him marry below his station, falls in love at first sight with a girl he sees on a bus. He follows her and discovers she is Margaret Sherwin, only daughter of a linen draper. He persuades her father to let him marry her secretly. He agrees on the condition, that, as his daughter is only seventeen, they live apart for the first year. At first the secret works, but then the mysterious Mannion, whose emotions cannot be read in his face, returns from abroad. On the last night of the year Basil follows Margaret and Mannion and discovers them in flagrante delicto. Basil attacks Mannion in the street and tries to murder him, but succeeds only in mutilating his face by pushing it into the fresh tarmacadam in the road. Mannion survives, recovers and swears revenge, and it is revealed that Basil's father indirectly caused Mannion's father to be hanged for forgery. Basil repudiates Margaret, but Sherwin threatens him with exposure unless he holds to his marriage. Basil confesses to his father, who disowns him, but his sister Clara stands by him. Basil's brother Ralph undertakes to buy Sherwin off, but meanwhile Margaret flees to Mannion, thereby acknowledging her guilt. Visiting Mannion in hospital, she catches typhus and dies. Basil, having been put on her track by Ralph, visits her on her deathbed. Basil flees from Mannion to Cornwall. The dénouement is worthy of Conan Doyle, set among whirlpools and cliffs near Lands End.