Agatha Christie

This is a comfort read--my copy is over 20 years old--but I keep going back to it.  I love a story with a hint of the impossible that has to be explained.  Gwenda comes back to England before her husband to buy a home, and then finds herself knowing things she can't possibly know about the home she's bought.  That includes the location of Helen's body in her front hall.   Gwenda has no memory