The novel opens with Carl Foster, a recently qualified doctor, coming to London to try and make his fortune. He meets a famous tenor, Signor Alresca, who suffers a dreadful injury backstage and Foster tends to him. He thus meets the lead soprano, Rosetta Rosa, and falls hopelessly in love with her.

Alresca takes Foster under his wing and they travel to Alresca's home in Bruges. It is clear to Foster that Alresca has some strange obsession. Foster also notices a stranger who seems to be dogging his footsteps.

Things take an even more sinister turn when Alresca inexplicably dies. . .