When a man murdered in a house near Edinburgh turns out to be a spy, Detective Sergeant Alistair MacRae wonders whether MI6 might be behind the killing, although there are plenty of other suspects who wanted the spy dead. When the spy's valet is murdered after having attempted to enter the guarded premises of the spy's house, MacRae is sure there is contraband material hidden in the building, but an expert insists there is no booty concealed anywhere and the guard is removed. When the house is then broken into and something taken from a cache in a skirting board, MacRae is furious until Detective Chief Inspector Ian Forsyth admits that he knew of the cache and is now able, by logical deduction, to arrive at the name of the killer. But, with MI6 involved, things are not that simple and events take a sinister turn before Forsyth explains all.