Dead Man's Chest: The maid's trunk is used by the killer to conceal the body of a coworker he murdered to serve as a scapegoat for the theft he committed himself.
Dude, Where's My Reward?: As a reward for the time he had already spent working on the case when they call him off, the Todds give Poirot a cheque for one guinea (worth a pound and a shilling).
Feet-First Introduction: Poirot is introduced in this manner: we get a close-up of Poirot's feet on the foot rest, then the camera moves slowly to his legs, all the way to his face when he is sitting on a chair.
Foreshadowing: Hastings discusses the disappearance of a bank clerk in an attempt to stimulate Poirot's mind with a compelling case. Poirot dismisses it, only for it to be the real crime that he ends up investigating later on.
Minor Crime Reveals Major Plot: The disappearance of a live-in cook from her employer's residence unveils the murder of a bank clerk and a plan to make off with fifty thousand pounds' worth of securities. At the end of the case, Poirot frames Mrs. Todd's Poirot cheque and hangs it on his wall as a reminder not to ignore the seemingly trivial.
Spotting the Thread: Poirot becomes suspicious of the killer the first time they meet, noticing a touch of glue on the side of his face. He had worn a false beard as part of his plan to get the maid out of the way
Start to Corpse: The episode takes a really long time to unveil the murdered clerk's body in the trunk, which is long even by Agatha Christie story standards. Justified in that we're not shown it's a murder mystery until more than halfway through.
Unwitting Pawn: Eliza Dunn turns out to have been manipulated by the perpetrator into leaving her employer's service with the prospect of her own property as bait. It's all part of a plan to use her trunk to hide the murdered clerk in while the killer makes a getaway.
