In the original story, Poirot gets involved in the case after Esmée Farquhar asks him to clear her fiancé Philip Ridgeway's name. In the episode, Poirot is involved right from the beginning, being asked to accompany Ridgeway as he takes the bond from London to New York.
In the original story, the real bonds were taken to New York by another ship, the Gigantic, which arrived earlier than the Olympic and allowed the villain to start selling them. In the episode, the bonds never even left England at all.
Adaptation Expansion: Mr Vavasour's role is expanded upon in the episode. Here he's the one who calls in Poirot to help safeguard the bonds as they're transported across the Atlantic.
Esmée Farquhar from the original story is now Esmée Dalgleish in the episode.
The name of the ship carrying Philip Ridgeway to New York is now the Queen Mary instead of the Olympia from the story.
Adapted Out: The character of Ventnor is excised from the episode, with his role and actions largely filled by the Canon Foreigner Miranda Brooks.
Bait-and-Switch: Poirot assures Ridgeway that he believes him to be innocent, then has him arrested as soon as they return to Southampton. This, however, was a protective measure, as it saved Ridgeway from being accosted by the loan sharks waiting at customs.
Blind Mistake: Mr. Vavasour's poor eyesight prevents him from realizing that the bonds were replaced with counterfeits before being transported to America.
Cover Identity Anomaly: Miranda Brooks, the glamorous woman Poirot and Hastings meet on the Queen Mary, automatically reaches to her chest when Poirot asks her the time...just like she would if she were a nurse with a watch pinned to her uniform.
Deliberate Injury Gambit: Mr. Shaw lets himself be hit by a car and be poisoned with a non-lethal dose of strychnine in order to let Ridgeway carry the bonds in his stead, avoiding suspicion in the process.
Disabled in the Adaptation: Mr. Vavasour is noted to have poor eyesight in the episode, while his eyesight is never noted upon in the original story.
Kansas City Shuffle: The villains' plan turns out to involve one. They arrange for Philip Ridgeway, a man known for having significant gambling debts to carry the bonds to America, and with one of them on board the ship deliberately misplacing them and pinning their loss on Philip. In reality the bonds were never on the Queen Mary; in fact they had never left England to begin with, and were safely with Mr Shaw all the time.
Sick Episode: Another one in a row for Hastings, as he's seasick during the trip on the Queen Mary.
Trapped by Gambling Debts: Ridgeway is set up to carry the bonds because he will be easy to accuse of stealing and selling them to cover his debts.
Two Aliases, One Character: Miranda Brooks, the woman in the cabin adjacent to Poirot's, is also Nurse Long, Mr. Shaw's caretaker and confederate.
