Hercule Poirot

Inspector Japp

Poirot and Japp have a professional working relationship as detective and police inspector, often collaborating on cases with mutual respect.

Flossie Monro

Flossie Monro is a client or witness who interacts with Poirot in the context of the investigation.

Madame Olivier

Madame Olivier is a formidable antagonist and member of the Big Four, opposing Poirot's efforts to dismantle the criminal organization.

Abe Ryland

Abe Ryland is a powerful member of the Big Four and a direct adversary to Poirot's detective work.

Mrs. Halliday

Mrs. Halliday is a client or person of interest in the case, interacting with Poirot as part of the investigation.

Dr. Savaronoff

Dr. Savaronoff is a scientist or expert consulted by Poirot in the course of the mystery.

Mr. Paynter

Mr. Paynter is a character involved in the plot, likely a suspect or witness interacting with Poirot.

Number Four

Number Four is a key member of the Big Four, a dangerous enemy working against Poirot.

Li Chang Yen

Li Chang Yen is a mastermind of the Big Four, a cunning and powerful adversary of Poirot.

Dr. Ridgeway

Dr. Ridgeway is a medical professional or expert who assists Poirot with forensic or scientific matters.

Halliday

Halliday is a character connected to the case, possibly a suspect or relative of a victim, interacting with Poirot.

John Ingles

John Ingles is an ally and friend who aids Poirot in his investigation against the Big Four.

The Unexpected Guest

Preparing to leave for South America on a lucrative case for Abe Ryland, but is drawn into the mystery of the Big Four when a stranger arrives at his flat.

II: The Man from the Asylum

Deduces the train diversion was a plot to get him out of the way; investigates the murder of Mayerling; realizes the killer is Number Four.

We Hear More About Li Chang Yen

Dismisses Hastings' hope of the fake attendant returning; visits Mr. Ingles to learn about Li Chang Yen; decides to travel to Dartmoor after reading Whalley's letter.

IV: The Importance of a Leg of Mutton

Leads the investigation, deduces the murderer's method using the frozen leg of mutton, and secures Grant's release.

V: Disappearance of a Scientist

Investigates Halliday's disappearance, deduces the Big Four's involvement, and decides to travel to Paris.

The Woman on the Stairs

Leads the investigation into Halliday's disappearance in Paris, interviews Madame Olivier, and deduces the involvement of the Big Four.

VII: The Radium Thieves

Remains in Paris after Halliday's release, sees through the Big Four's bribery attempt, and plans to protect Madame Olivier's radium.

In the House of the Enemy

Poirot suspects Ryland is Number Two, devises the infiltration plan, and later deciphers the coded message, though the trap backfires.

IX: The Yellow Jasmine Mystery

Poirot is investigating the Paynter case, using it to take a break from his obsession with the Big Four. He remains confident and methodical.

X: We Investigate at Croftlands

Investigates the death of Mr. Paynter, deduces the significance of 'Yellow Jasmine' as a poison, and identifies Dr. Quentin as the murderer.

XI: A Chess Problem

Dines with Hastings and Japp; deduces the murder method involving an electrified chess piece and links it to the Big Four.

The Baited Trap

Discusses the investigation with Hastings, then leaves the room; Hastings leaves a sign for him.

The Mouse Walks In

Deciphers Hastings' warning signs, arrives prepared with a smoke bomb and police, rescues Hastings.

XIV: The Peroxide Blonde

Leads the investigation, deduces Number Four is an actor, and vows revenge after Flossie Monro's death.

XV: The Terrible Catastrophe

Reveals the Big Four to officials, prepares for his death, and is killed by a bomb in his lodgings.

Number Four Wins a Trick

In hiding in the Ardennes, Poirot plans to resurrect himself and gather the Big Four together for a final strike. He interprets Hastings' account of Ingles's servant's dying words to deduce the meeting place at Karersee.

In the Felsenlabyrynth

Revealed to have been impersonating his 'twin brother' Achille; orchestrates the cordon and rescue, and later explains his full plan.