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 visits his birth mother's old house in London, and encounters fugitives from an anti-apartheid demonstration.
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 the truth?
In his final term at school, Billy learns his birth father, Jerry Toth, defected to Britain in 1955 and married, then later divorced, a glass heiress. Along with his friend Spike and other classmates, he has a run-in with a local bike gang.
An unannounced visit to his father's ex-wife in Scotland reveals that Billy has a older half-sister, Pamela. He learns little, other than 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 host's son fulfill a family tradition.
Spike, Billy's best friend from school, arrives unexpectantly. 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 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.
Mr Whitaker is taken ill during a chess match with Billy. Pricey fears it may be a stroke.
In Saltzburg 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.
Billy's relationship with Julie, a fellow student, threatens his hard-won place at Zuckmeyer Academy. Mr Whitaker and Dr Jolland travel to Salzburgh to find out why.
Whilst in Bamburgh with Julie, she and Billy run into a free spirit called Michael, who then proceeds to come between them. Gunter Walser and Mr Whitaker arrive with news about Helga Gruber.
During a visit to the cottage, Pricey reveals a little of her past, while Mr Whitaker's acceptance of an invitation to go sailing in Billy's boat, the Amadeus, inadvertently thwarts an attempt of Billy's life.
Through a local villager, Billy learns what Karl Gruber was responsible for the boat explosion. He decides to return to the Salzburg music academy, not just to resume flute lessons, but also in the hope of luring Gruber out into the open.
Billy encounters a mother and son in Saltzburg who are about to become the latest victims of Kurt Gruber.
Billy and Vincent meet Mrs Dalgleish at the Royal Albert Hall, where Mrs Dalgleish has a message from Kurt. "Stop looking for him." After being told he already knows him by another name, Billy finally realizes who Kurt is.
Things come to a head in the Austrian Alps, as Billy confronts Kurt Gruber for the final time.
