The A B C Murders -by Agatha Christie

M. Hercule Poirot showed a letter to his friend Captain Hastings. The letter was from a murderer, who informed poirot about the next murder he was going to commit and challenge Poirot to stop the murder. But poirot failed to stop the murder. Two more murders happened and happened alphabetically:

A is for Andover and Mrs.Ascher battered to death.

B is for Bexhill and Betty Barnard strangled.

C is for Sir Carmichael Clarke clubbed and killed.

Could poirot stop the killer at D?