Inspector Hartnell and Sergeant Johnson are called out to investigate a routine break-in at the home of a prominent but aging mathematician, Frederick Leston. Strangely, it would appear the burglars took nothing of value-just a simple folder. Even Leston can't understand why one folder would be of such interest to criminals-or so he claims.

Hartnell and Johnson aren't convinced and believe the old man might be hiding something, but they have no idea they're about to jump head-first into a mysterious situation that could get them both killed. They soon find themselves racing around Great Britain and France, trying to make sense of a bizarre set of circumstances, all seemingly related to Leston.

During their investigation, the policemen have a feeling they're being followed, and they also suspect Leston has lied to them. There must be something to the odd burglary and not just a botched attempt for petty thieves to get rich. When murder ups the stakes, this case turns deadly but goes to prove that no one can escape the past.