A Shot at Nothing — Roger Ormerod

Philipa Lowe is in search of a house, but her friend Oliver does not approve, particularly of the one she dearly wishes to see. In spite of his reluctance, she goes ahead, and on first sight of it is full of enthusiasm. Oliver's reluctance is soon explained, as this was the house where a murder took place. Six years before, Clare Steadman was committed to prison for the murder of her husband. Philipa is intrigued when she discovers that Oliver himself was intimately involved. It is when Oliver declares that he believes Clare to have been innocent that Philipa interests herself in the evidence -- for how could Clare, with the doors locked against her, and the window jammed by her own efforts with a shotgun, have reached her husband, in order to make use of the second barrrel? And at what was the third shot fired? At nothing?