Hot Money by Dick Francis

Malcolm Pembroke never expected to make a million pounds without making enemies. Nor did he expect his latest wife to be brutally murdered. All the clues suggest the killer comes from close to home - but after five marriages and nine children, that still leaves the field wide open.

When he finds his own life in danger, Pembroke entrusts his safety to his estranged son, Ian, an amateur jockey; and through him discovers a compulsive new outlet for his financial expertise.

Soon he's playing the international bloodstock market for incredible stakes. Not the safest bet for a man on the run from avaricious relatives. Particularly when one of them's got a bomb...