Francis McNab, crime reporter and amateur criminologist, receives a letter from Ann Cardew asking him to investigate her father's erratic and alarming behavior. Ann is disturbed by such odd incidents as her father repeatedly checking his shoes and carefully shaking them out before putting them on. He is also often seen staring out the windows of their home, nervously scanning the horizon for something -- or someone. Before McNab has chance to even interview Cardew, however, the man drops dead on his front lawn. The circumstances appear mysterious, but there is no sign of foul play at all. The coroner's verdict seems sure to be death from natural causes, until the inquest is adjourned for one week when the police insist on time to gather more evidence. McNab and reporter Godfrey Chance join in the investigation to prove that Cardew's death was "one of the most diabolically ingenious murders in criminal record."