Agatha Christie published The Third Girl in 1966. Many think the late Christies are inferior books. Others think Christie’s late novels were affected by Christie’s alleged Alzheimer’s. I found The Third Girl uneven, but the solution is clever (Christie stumped me). A young girl shows up at Poirot’s doorstep and says, “I may have committed a murder.” Then, she disappears. Mystery novelist Mrs. Oliver, Christie’s surrogate, shows up and gets bashed on the head. Tonight PBS Masterpiece Mystery broadcasts the TV version of The Third Girl. I’ll be watching.