'I' said the sparrow

Who killed Le Maitre? The clues are all there and like any good whodunnit this has an unambiguous answer. But first I would question the basic premise... Who said he was dead... maybe he escaped dressed as an abo or his own child... Nevertheless the number of dead bodies is evidence enough of an hideous crime! So who is responsible. A girl I knew once suggested I might enjoy 'Murder on the Orient Express.' I had never read the book or seen the film and I had not even discussed it with my sister who was a huge fan, though I disapproved ever since '10 little niggers' gave me nightmares. 'You'll never guess the end.' she said. I did. =====