
The murderer in that case has long been convicted and executed but the ransom moneys were never recovered, a known accomplice never captured, and both the Armstrong parents have since tragically died. Poirot quickly learns that the victim was not who he presented himself to be and has a connection to a five-year-old American kidnapping and murder case of infant Daisy Armstrong, murdered in spite of the fact that her parents had paid the requested ransom. At the time the victim is found, the train is unexpectedly stopped and delayed due to snow in remote Yugoslavia, which may be problematic for the murderer in getting away now that Poirot is on the case, which he is doing as a favor to Bianchi as not to get the Yugoslav police involved.

At least one of them has reason to be concerned, as later, another first class passenger, who earlier in the trip asked Poirot to provide protection for him due to several death threats, is found murdered in his stateroom by multiple stabbings. Some of the first class passengers seem concerned about Poirot's presence on the train.

Regardless, famed and fastidious Belgian detective, Hercule Poirot, who needs to get back to London immediately, is able to secure last minute passage in the compartment with the assistance of his friend, Signor Bianchi, one of the directors of the train line who is also making the trip. The first class compartment of the December 1935 departure of the Orient Express from Istanbul is full, unusual for this time of the year.
