The A.B.C. Murders

When Alice Ascher is murdered in Andover, Hercule Poirot is already on to the clues. Alphabetically speaking, it's one down, twenty-five to go.
There's a serial killer on the loose. His macabre calling card is to leave the ABC Railway guide beside each victim's body. But if A is for Alice Asher, bludgeoned to death in Andover; and B is for Betty Bernard, strangled with her belt on the beach at Bexhill; then who will Victim C be?