They Can't Hang Caroline — Roy Vickers

Inspector Curwen and Hugh Stanton were faced with the most challenging case of their careers. Herbert Gretton had been found murdered in the gloomy old mansion, Whiddonmere Hall, and although motive and malice were not lacking in the various suspects, the murderer had concealed his or her tracks with ingenuity. Was the crime committed by Caroline, Gretton's wife, or by Mrs Whiddon, the owner of the Hall, who alone knew of the secret chamber in which the murdered man was found. And who was Hairyhands, who visited Caroline on the night of the murder...?