What is the connection between the beady private eye crooning soft songs at the Laguna, and the disfigured man struggling for his sanity in a hospital bed?

Why does the small boy spy from the top of the tree, and who is the naked girl dragged out of the murky Thames? The clues are bloody and tangled, but the singing detective knows that the answers will eventually jump out of him as long as he keeps singing the right tunes.

While in hospital with psoriasis, Marlow thinks back to the war when he was a little boy, and remembers seeing his mother having illicit sex in the Forest of Dean. His memories, his 30s style gumshoe fiction and his disease weave him an altered reality.