Set in 1936 in Belgium and Ceylon, Smoke Portrait traces the development of an unlikely friendship between a young Belgian teenager, Marten Kuypers, and Glen Phayre, an Englishwoman in her twenties. Glen has left England to live on her aunt's tea plantation in Ceylon, where she embarks on the task of writing charitable letters to a Belgian prisoner. But the letters go astray, and are received instead by Marten, eager to discover the wide world outside his small village, and desperately missing his older brother Krelis, who has vanished and is presumed dead.
Marten decides to reply to Glen in the guise of the grown-up prisoner she is expecting to hear from, and as their correspondence evolves, they both assume identities that, while false in many respects, remain true to their own selves in other ways. Gradually they come to depend on each other, and their pen friendship proves to be crucial when events in their real lives take on a darker, more threatening turn in the shadow of the impending world war.