Six months before his 18th birthday, Billy Stanyon's mother and father die in a sailing accident. They leave him a flute, some letters, and the knowledge that they were not his biological parents.

Billy visits his birth mother's old house in London, where he encounters fugitives from an anti-apartheid demonstration.

Billy meets the mysterious Vincent Whitaker, who accompanies him 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 the truth?

Now in his final term, Billy learns his birth father, Jerry Toff, defected to Britain in 1955 and married, then later divorced, a glass heiress. Along with his best mate Spike and other classmates, he has a run-in with a local motorcycle gang.

An unannounced visit to his father's ex-wife Charlotte in Scotland reveals that Billy has an older half-sister named Pamela. He learns little other than that his father and Charlotte met when he worked as a stable lad on her father's estate.

Billy seeks help to pursue his goal of becoming a professional flautist. Meanwhile, a runaway family take refuge in his seaside cottage.

Billy visits France where he learns more about his parents and helps his hosts' son fulfill a family tradition.

Spike arrives unexpectedly. Billy offers to put him up for the night, causing friction between him and Mr Whitaker.

Frau Gruber sends Billy his father's ring, prompting him to return to Lake Chemsee for answers. However, she will only tell him that the search for his natural father only spells peril.

Billy befriends a teenage runaway who stays the night with him at his seaside cottage. Meanwhile, Mr Whitaker receives an unexpected home visit from Miss Price.

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 parents.

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.