Following the disbanding of the Network, the international crime cartel headed by Modesty Blaise, her former right hand man Willie Garvin is at a loss as to how to channel the myriad skills he used in his six years in service of the Princess (as Willie affectionately refers to Modesty), and after getting involved in a South American revolution and consequently ending up in some pesthole prison he's pretty much shit outta luck. Fortunately for Willie, his plight is known to Sir Gerald Tarrant, head of a British intelligence organization, and knowing of Willie's value to Modesty he informs her of the situation. When he gives the information to Modesty, Tarrant is does so telling her that there are no strings attached to his gift, thereby winning her gratitude and promised help should he need it in the future. After rescuing Willie, Modesty's adventure — and subsequent frequent involment in Tarrant's cloak and dagger world — begins in earnest as she and Willie take on Gabriel, a crook with a diamond-thieving agenda who comes off as Ian Fleming-light, and all you really need to know about the outcome is that Modesty and Willie put the kibosh on his scheme.
Apparently written as a screenplay featuring his newspaper comic strip characters, Peter O'Donnell's first Modesty Blaise novel isn't bad, but it can't measure up to the later entries in the series thanks to it being just another in the flood of espionage stuff that was glutting the market at the time, albeit with outstanding protagonists. And the screenplay was distorted almost beyond recognition as the appalling Joseph Losey film of 1966, a movie that sucked out loud just about as much as it's possible for a film to suck out loud. Trust me when I urge you to skip it, even as a camp curiosity.