Robbie Parsons is one of London's finest, a black cab driver who knows every street, every theatre, every landmark in the city by heart. In his backseat is a man with a gun in his hand - a man who shot Robbie's previous pair of customers point-blank in front of the Artemis Club, a rarefied art gallery-cum-casino, then jumped in and ordered Parsons to drive. As the killer eventually escapes to Nairobi with ten-year-old Patty Haigh - one of a crew of stray kids who serve as the cabbies' eyes and ears at Heathrow and Waterloo - in pursuit, superintendent Richard Jury comes across the double-homicide in the Saturday paper. Two days previously, Jury had met and instantly connected with one of the victims, a professor of astrophysics at Columbia and an expert gambler. Jury considers the murder a personal affront and is soon contending with a case that takes unexpected turns into Tanzanian gem mines, a closed casino in Reno, and a pub that only London's black cabbies, those who have 'the knowledge,' can find.