"Among all of Carr’s ingenious crime scenes, the present case is one of his best known: a dead man is found strangled in the middle of a clay tennis court, just after a storm. In the damp dirt, there is one set of footsteps―his own―leading back to the grass; the court is otherwise untouched. There are no trees above from which the body may have fallen and no other visible means by which it may have been transported to its final resting place....