The Mystery of the Blue Train · Character

Derek Kettering

A charming, debt-ridden husband whose careless wit and convenient alibi make him the most obvious and least comfortable suspect.

major

Also known as Mr. Kettering, Derek, M. Kettering, Monsieur Kettering

First appearance: In Curzon Street

As a major figure in The Mystery of the Blue Train, Derek Kettering is not background color—the story leans on what they do once the chapter opens.

Ruth's estranged husband, whose presence on the train raises suspicion and conflict.

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Derek Kettering moves through the story with the easy manners of a man who has never had to earn anything, and the mounting debts of one who has spent everything anyway. He is travelling on the same train as the wife he is about to lose, accompanied by the dancer Mirelle, and his flippant remark that dying on a train causes 'all sorts of legal and international complications' lands with grim irony. Van Aldin despises him; the police watch him; and his genuine shock at the news sits uneasily beside the two million pounds he stands to gain.

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See Derek Kettering in In Curzon Street

Character Web

19 connections

A slice of how Derek Kettering sits in the book — open the reader for the full interactive map.

Relationship types

Romantic
Rivalry
Family
Other

Character groups

Key suspects and witnesses
Supporting cast and background
Protagonist

+14 more in the full Character Web

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Narrative arc

Story tension across the book — this chapter sits in Exposition.

Setup
Escalation
Breaking point
Aftermath
Closing

In this scene, the emotional and psychological peak occurs when Poirot’s tone shifts to an uncharacteristic se…

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Relationships

Katherine Grey
romantic · positive
Derek is drawn to Katherine's calm and genuine nature, developing romantic interest after… How this plays out →
Hercule Poirot
rivalry · negative
Ruth Kettering
family · negative
Comte de la Roche
rivalry · negative
Hercule Poirot
rivalry · negative
Ruth Kettering
family · negative
Hercule Poirot
rivalry · negative
Katherine Grey
romantic · positive
Derek is drawn to Katherine's calm and genuine nature, developing romantic interest after… How this plays out →
Katherine Grey
romantic · positive
Derek is drawn to Katherine's calm and genuine nature, developing romantic interest after… How this plays out →
Comte de la Roche
rivalry · negative
Ruth Kettering
family · negative
Comte de la Roche
rivalry · negative

Katherine Grey
Derek is drawn to Katherine's calm and genuine nature, developing romantic interest after his wife's death.
Hercule Poirot
Derek is initially hostile and suspicious of Poirot's investigation, fearing he will be accused.
Ruth Kettering
Derek and Ruth are estranged married couple, with deep resentment and financial conflicts.
Comte de la Roche
The Comte and Derek are bitter rivals over Ruth and her fortune, each suspecting the other of murder.
Hercule Poirot
Derek is initially hostile and suspicious of Poirot's investigation, fearing he will be accused.
Ruth Kettering
Derek and Ruth are estranged married couple, with deep resentment and financial conflicts.
Hercule Poirot
Derek is initially hostile and suspicious of Poirot's investigation, fearing he will be accused.
Katherine Grey
Derek is drawn to Katherine's calm and genuine nature, developing romantic interest after his wife's death.
Katherine Grey
Derek is drawn to Katherine's calm and genuine nature, developing romantic interest after his wife's death.
Comte de la Roche
The Comte and Derek are bitter rivals over Ruth and her fortune, each suspecting the other of murder.
Ruth Kettering
Derek and Ruth are estranged married couple, with deep resentment and financial conflicts.
Comte de la Roche
The Comte and Derek are bitter rivals over Ruth and her fortune, each suspecting the other of murder.

Relationship notes

How these ties play out is in the reading companion — open the free preview.

See Derek Kettering in In Curzon Street

In the story

Derek Kettering appears across 22 companion beats. Open any chapter in the free preview to see the notes beside the text.

The Mystery of the Blue Train
Ruth's estranged husband, whose presence on the train raises suspicion and conflict.
In Curzon Street
Mentioned as Ruth's unfaithful husband who is seeing Mirelle; Van Aldin plans to meet him the next morning.
A Useful Gentleman
Visits Van Aldin; argues against the divorce, hints at Ruth's own secrets, and warns Van Aldin to seek frankness between father and daughter.
VI: Mirelle
Visits Mirelle after a tense interview with Van Aldin; defends his wife's honor against Mirelle's insinuations.
An Offer Refused
Derek books a Blue Train ticket under the name Pavett, contemplates his financial troubles, and refuses Van Aldin's bribe of one hundred thousand pounds.
At the Villa Marguerite
Derek arrives for dinner at the villa, unaware of his wife's murder. He recognizes Katherine from previous encounters and is later summoned by the Prefect of Police, showing his ignorance of the crime.
Van Aldin Gets a Telegram
Reported by Mr. Goby to have left London for the Riviera on the Blue Train the previous morning.
XVI: Poirot Discusses the Case
Discussed as the husband who refused a divorce bribe, traveled with Mirelle, and inherits two million pounds from Ruth's death.
An Aristocratic Gentleman
Questioned by the magistrate and Poirot; denies seeing his wife on the train and reveals knowledge of the rubies.
XVIII: Derek Lunches
Derek is moody and drinks cocktails before being approached by Mirelle. He rejects her and invites Katherine Grey to lunch.
An Unexpected Visitor
Mirelle accuses Derek Kettering of murdering his wife, claiming he boasted of it beforehand and traveled on the same train to kill her.
Katherine Makes a Friend
Discussed by Katherine and Lenox; Katherine recalls his remarks about his wife's death and his attractiveness.
At the Tennis
Appears reckless and angry; questioned by Poirot about the cigarette case.
A New Theory
Implied as a possible suspect; Poirot suggests he may have been the man talking to Ruth at the Gare de Lyon.
XXIV: Poirot Gives Advice
Seen speaking earnestly with Katherine Grey; later confronts Poirot about his feelings for Katherine and his break with Mirelle.
XXV: Defiance
Confronts the Comte de la Roche and later Mirelle, refusing blackmail and asserting his innocence.
A Warning
Derek confesses to Katherine that he entered his wife's compartment on the train, but denies murdering her, and declares his love for her.
Interview with Mirelle
Accused by Mirelle of murdering his wife; she claims to have seen him leave Ruth's compartment before the train reached Lyons.
XXVIII: Poirot Plays the Squirrel
Arrested for the murder of his wife; Lenox is informed of this by Poirot.
XXXI: Mr. Aarons Lunches
Mentioned as being in prison, suspected of murdering his wife on Mirelle's account.
XXXII: Katherine and Poirot Compare Notes
Mentioned as the prime suspect; Poirot questions whether he would have disfigured the victim's face.
By the Sea
Released from custody and has left Nice for St. Mary Mead.

Chapter companion notes

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See Derek Kettering in In Curzon Street

See Derek Kettering in The Mystery of the Blue Train