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The Third Girl by Agatha Christie – A twisty Poirot mystery that will keep you guessing

Agatha Christie's The Third Girl is a gripping mix of psychological tension and classic detective work, featuring Hercule Poirot. When a young woman claims she’s a murderer but disappears before giving details, Poirot is drawn into a web of deceit, family secrets, and manipulation. But does this novel live up to Christie's best? Let’s investigate!

What makes The Third Girl a Must-read?

Agatha Christie's 35th Hercule Poirot novel, The Third Girl, stands out from the detective’s earlier adventures. It is not a traditional whodunit set in a country house or an exotic location. Instead, it delves into the complexities of the human psyche. Set in 1960s London, the story follows a young woman, Norma Restarick, who is unsure whether she has committed a murder. Poirot must navigate the uncertainties of her fragmented memories, unreliable narratives, and modern psychology.

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But does The Third Girl live up to the brilliance of Christie’s earlier masterpieces? And how does it fare in today’s crime fiction landscape?


What is the story about?

An unexpected visitor

One morning, Hercule Poirot is enjoying his breakfast—a perfectly buttered brioche and a rich cup of chocolat—when his routine is unexpectedly disrupted. A young woman named Norma Restarick enters and bluntly declares, “I think I have committed a murder.” Before Poirot can question her, she vanishes as abruptly as she arrived.

Poirot, intrigued yet skeptical, reaches out to his good friend, the crime writer Ariadne Oliver. Mrs. Oliver, who has met Norma before, insists that something is truly amiss. Together, they embark on an investigation that leads them deep into the troubled life of the elusive "third girl."

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Who is the Third Girl?

Norma shares a London flat with two other women:

  • Claudia Reece-Holland, a poised and efficient personal secretary.
  • Frances Cary, an independent, sharp-witted artist.

Norma is referred to as the "third girl" because, in her own home, she is the odd one out—restless, insecure, and emotionally fragile. She has a complicated family history, a mysterious artist boyfriend, and a father who has reappeared after years of absence.

The investigation unfolds

As Poirot digs deeper, he discovers rumors swirling around Norma—whispers of madness, instability, and even murder. However, Poirot is not one to rely on gossip. He needs facts, and the more he uncovers, the more the mystery thickens.

  • Is Norma truly guilty of murder, or is she being manipulated?
  • Is someone trying to frame her, or is her mind playing tricks on her?
  • And most importantly, what dark secrets are hidden in her past?

As the case progresses, Poirot peels back the layers of deception, leading to a shocking revelation that only he could unravel.

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Who are the main characters in The Third Girl?

Hercule Poirot – The ageing detective with an undimmed mind

Unlike earlier Poirot novels, The Third Girl highlights the detective’s age. Poirot is no longer the sprightly investigator of the 1920s and 30s. He is reflective, sometimes doubting whether the fast-changing modern world still has a place for his meticulous methods. Despite this, his mind remains as sharp as ever, proving that age does not diminish genius.

Ariadne Oliver – The writer who thinks faster than she speaks

A delightful recurring character, Ariadne Oliver is Christie’s humorous self-insert. She is an eccentric but sharp-minded crime novelist, often exasperated with her own writing process. In The Third Girl, she provides comic relief while also playing a crucial role in assisting Poirot.

Norma Restarick – The girl who might have killed

Norma is one of Christie’s most psychologically complex characters. She is deeply troubled, haunted by self-doubt and unreliable memories. Her struggle with her own mind makes her an unusual and compelling figure in the novel.

David Baker – The brooding artist

David Baker is Norma’s enigmatic boyfriend—charismatic, mysterious, and possibly dangerous. His influence over Norma raises suspicion, but is he a genuine threat or just a red herring?

Frances Cary – The independent roommate

Frances, Norma’s roommate, is a fascinating character. Calm and rational, she seems to be the most stable of the trio. However, Poirot knows better than to trust outward appearances.

Claudia Reece-Holland – The cool and collected one

Claudia appears professional and reserved, but does she know more about Norma’s troubles than she lets on? Her role in the story is subtle yet significant.


Does The Third Girl live up to Christie's best works?

While The Third Girl is an enjoyable read, it does not quite reach the heights of Murder on the Orient Express or The Murder of Roger Ackroyd. Here’s why:

  • A Slower start – The novel takes time to build momentum. Unlike Christie’s usual fast-paced storytelling, this book lingers on psychological elements.
  • A Different Tone – The psychological thriller aspect is intriguing but may not appeal to fans of traditional whodunits.
  • A More Ambiguous Mystery – Unlike the clear-cut murder cases of Christie’s best works, this novel plays with the idea of whether a crime has even been committed at all.

Despite these differences, The Third Girl remains a fascinating Poirot novel, especially for those interested in the intersection of crime fiction and psychology.


What are the best quotes from The Third Girl?

One of the most poignant lines in the book is:

"A man, madame, should not grow old, unless he is something."

This reflects Poirot’s own doubts about ageing in a modern world that no longer seems to value his methods.


Which Agatha Christie books should you read in 2025?

If you’re new to Christie or want to revisit her classics, here are some must-reads:

  1. The Murder of Roger Ackroyd (1926) – A groundbreaking novel with a shocking twist.
  2. Murder on the Orient Express (1934) – Perhaps the most famous Poirot mystery.
  3. The ABC Murders (1936) – A brilliant serial killer novel.
  4. Death on the Nile (1937) – A glamorous murder set on a cruise ship.
  5. Five Little Pigs (1942) – A psychological mystery told through different perspectives.
  6. The Hollow (1946) – A deeply emotional mystery with a complex ending.
  7. The Labours of Hercules (1947) – A collection of Poirot short stories.

These books remain bestsellers, proving that Christie’s genius is timeless.


Where does The Third Girl fall short?

While The Third Girl is an engaging read, it has a few drawbacks:

  • A Slow First Half – The pacing could have been tighter.
  • Norma’s Passivity – She is a complex character, but her lack of agency can frustrate readers.
  • An Abrupt Ending – The conclusion, though clever, feels slightly rushed compared to Christie’s best.

Despite these minor flaws, the novel still provides a satisfying read, especially for Poirot fans.


Should you read The Third Girl?

Yes, but with adjusted expectations. It is a different kind of Poirot novel—more psychological, slower-paced, but still intellectually satisfying. If you enjoy mysteries that focus on the human mind, this one will intrigue you.


FAQs about The Third Girl

1. Is The Third Girl a standalone novel?
No, it's the 35th Hercule Poirot novel, but it can be read independently.

2. How does The Third Girl compare to Christie's other books?
It’s more psychological, focusing on mind games rather than traditional clues.

3. Is the ending satisfying?
Yes, Poirot’s deductions are as sharp as ever, though the final reveal feels a bit rushed.

4. Is this book a good introduction to Agatha Christie?
Not really. If you're new to Christie, start with Murder on the Orient Express.

5. Where can I buy The Third Girl?
It’s available in paperback from HarperCollins, as well as in eBook and audiobook formats.


Tushar Mangl writes on books, investments, business, mental health, food, Vastu, leisure, and a greener, better society. Speaker, author of Ardika and I Will Do It.

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