Knife Edge — Donald MacKenzie

Neil MacFarlane, a gentleman gambler on the French Riviera, is caught in a run of bad luck. His only chance to recoup his losses lies in gaining admittance to a private game, far from the eagle-eyed supervision of the Cannes casino croupier. But by the time he has succeeded in extracting an invitation from the rich Whitakers to dinner and a friendly game at their house, he is completely cleaned out. His hotel room is locked against him, and the angry manager refuses to open it until his bill is paid. Then an enigmatic Englishman makes him a curious offer, which he accepts - and is drawn into a game in which the stakes are much higher than he could ever have imagined . . .