Elephants Can Remember - Agatha Christie

Hercule Poirot is determined to solve an old husband and wife double murder that is still an open verdict... Hercule Poirot stood on the cliff-top. Here, many years earlier, there had been a tragic accident., This was followed by the grisly discovery of two more bodies - a husband and wife - shot dead. But who had killed whom? Was it a suicide pact? A crime of passion? Or cold-blooded murder? Poirot delves back into the past and discovers that `old sin leave long shadows'.