Agatha Christie 
Double Sin 

Poirot and Hastings go on vacation. On the bus they meet Mary Durrant, who works with her aunt in an antique shop and travels, like them, to Charlock Bay carrying a valuable set of miniatures that she will sell to an American collector. Everyone is staying at the Anchor Hotel. Mary discovers unpacking her suitcase that it has been broken and the miniatures are no longer there. Desperate, she asks Poirot for help. The first thing the detective does is telephone the buyer, Mr. Wood, who claims that half an hour earlier someone in the name of Elizabeth Penn, Mary Durrant’s aunt, sold him the famous miniatures for GBP500. Can Poirot discover the truth?