An old librarian, Professor Columbus, wants to go to the sea once in his lifetime. So he buys a big ship and takes a boat trip across the North Sea to London, accompanied by a bunch of stoned hippies, and chased by the police.

Painter Peter Hartman is arrested at the scene of a murder. He soon turns out to have ties to the victim's young widow. As Inspector Stroomer begins to unravel the mystery, two very different sides of the story are presented to him. Now it is up to Stroomer to find enough photographic evidence to make out which version is the truth.