Robbie Parsons is one of London's finest, a black cab driver who knows the city by heart. In his backseat is a man with a gun in his hand-a man who brazenly committed a crime in front of the Artemis Club then jumped in and ordered Parsons to drive. As the criminal eventually escapes to Nairobi, Detective Superintendent Richard Jury comes across the case in the Saturday paper. Two days previously, he had met and connected with one of the victims, a professor of astrophysics at Columbia and an expert gambler. Feeling personally affronted, Jury enlists Melrose Plant, Marshall Trueblood, and his whole gang of merry characters to contend with a case that involves Tanzanian gem mines, a closed Reno casino, and a pub that only London's black cabbies who have the knowledge can find.