Murder Is Easy - 1982 - 6/10

Middling Agatha Christie mystery of serial killer among the gentry.
American computer expert (probability expert) meets elderly woman on train.
She confides there have been several killings in her hamlet, another is imminent, then before she can reach Scotland Yard, she is killed! What are the odds?
Naturally, the Yank decides to play detective.
Stodgy, old-fashioned, resembling Murder, She Wrote, right down to the yellow credits.
The older players are better in this (the romantic leads have NO chemistry), and this provides a nice glimpse at Olivia de Havilland in one of her final roles.
Plot later re-fashioned into a Miss Marple story, but it is not canon proper.