The Mystery of the Blue Train is a classic detective novel set against the backdrop of international luxury travel in the late 1920s. When a wealthy American heiress is found murdered aboard the famous Blue Train en route to the French Riviera, Hercule Poirot becomes involved in a case shaped by privilege, secrecy and ambition. The confined elegance of the train conceals rivalries, betrayals and motives that extend far beyond the journey itself. As the investigation unfolds, appearances prove unreliable and wealth offers no protection from suspicion. Each passenger carries a version of the truth, and the crime reveals how easily desire and desperation can coexist beneath polished surfaces. This annotated edition pairs the original novel with chapter-by-chapter summary notes that clarify the investigation, trace character relationships and illuminate Christie's careful manipulation of setting and misdirection. First published in 1928, The Mystery of the Blue Train reflects Christie's growing interest in glamour, international settings and psychological motive, while retaining the controlled logic of the classic Poirot mystery.