When Richard Hannay simply picks up a baby's rattle in Regent's Park, he inadvertently sparks off a trail which leads to espionage and murder. From the moment he hands the rattle to the baby's nurse, he is trapped in a web of intrigue. The 'nannie' is in fact a secret agent with orders to smash an espionage organisation intent on smuggling out of the country plans of vital importance to Britain. But then she is murdered. All Hanay knows is that the 'brain' of the organisation is to be found in Scotland. But what is the mystery of the last words uttered by the 'nannie' before her death... 'the 39 steps'?