In the Frame by Dick Francis

Charles Todd—a renowned painter of horses—is shocked when he turns up at his cousin Donald’s house for a weekend visit to find his cousin’s young wife dead on the floor—and Donald the police’s prime suspect. Determined to prove Donald’s innocence, Todd trails a set of clues from England to Australia to New Zealand, only to realize that someone is trailing him. Someone with every intention of taking him out of the picture for good…