El Testigo Mudo

"Miss Arundell is a wealthy old spinster whom her nephews wish to see dead so they can relieve themselves of their financial worries. When he has an accident when he falls down the stairs, everyone blames it on the rubber ball left by Bob, his dog. But the old woman is distrustful, and thinks that they have tried to murder her. On April 17 he writes a letter to Poirot requesting his help, but he does not receive it, mysteriously, until June 28th, Miss Arundell has been murdered, and the only witness to the crime is Bob, her beloved pet."--