Six months before his eighteenth birthday, Billy Stanyon's mother and father die in a sailing accident. They leave him with a flute, some letters, and the knowledge that they were not his natural parents.
Billy and Mr Whitaker fly to Munich where an ex-client of Whitaker's takes them to Lake Chiemsee. Frau Gruber tells Billy his mother was killed whilst crossing the Hungarian border, along with her own son. But is she telling him the truth?
In his final term at school Billy learns his birth father, Jerry Toff, defected to Britain in 1955 and married, then later divorced, a glass heiress. Along with Spike and other classmates he has a run-in with a local motorcycle gang.
An unannounced visit to his father's ex-wife in Scotland reveals that Billy has an older half-sister, Pamela. He learns little other than that his father and Charlotte met when he worked as a stable lad on her father's estate.
Frau Gruber sends Billy his father's ring, prompting him to return to Lake Chemsee to find out why. She will only tell him that it's dangerous for him to continue the search for his natural father.
Billy befriends a teenage runaway who stays the night with him at his seaside cottage. Meanwhile, Mr Whitaker receives an unexpected home visit from Pricey.
An unannounced visit by Mrs. Dalgleish, originally from Hungary but now the colourful and wealthy widow of a financial tycoon, affords a few more details about Billy's birth mother and father.
In Salzburg to audition for a music scholarship, Billy finds himself followed by Hilda Gruber. Instructed to kill him, she chooses instead to tell him that it was his father who died fleeing Hungary, not Karl Gruber.
