"The truth is always stranger than fiction!"
— Katrielle Layton

Katrielle "Kat" Layton is the protagonist of Layton's Mystery Journey: Katrielle and the Millionaires' Conspiracy and Layton Mystery Detective Agency: Kat's Mystery-Solving Files, and the daughter of Professor Hershel Layton. A "riddle-solving detective" and founder of the Layton Detective Agency, Kat takes on various cases brought to her by fellow Londoners in the hope of finding her missing father. She is assisted in her investigations by her devoted assistant Ernest Greeves and a talking dog named Sherl.



Kat is a young woman with brown curly hair, rosy cheeks and blue eyes. Usually, she wears a red dress with a black bow, black leggings, and blue shoes, and adds a tan coat and a hairband with a top hat on it when in the field. She also has a wide range of other outfits, which can be changed in game. To sleep, she wears a pale yellow nightgown.


Katrielle is an eccentric but humourous young lady, with an active imagination in full employ when solving puzzles and crimes. She relies largely on her "miraculous instinct" to solve mysteries and jokingly mocks investigators that rely solely on concrete evidence, prompting some spectators like Sherl to credit Kat's success to dumb luck. She'll often posit highly imaginative or complex explanations for mysteries, unlike her father who is more grounded in realistic scenarios. This all leads some, such as Emiliana Perfetti, to not take her seriously as a detective.

Kat often appears unflappable in the face of the most bizarre mysteries, not being impressed or surprised at all that Sherl was talking, and speaking very nonchalantly about her father's past cases. She also does not seem to question her father's puzzles but is nevertheless close to him. Despite this, she can be rather intuitive, much like her father, and uses her intelligence to her advantage.

However, in the anime as connected to the game progressing, Kat become quick tempered and easily scares Ernest.

Kat also displays an insatiable appetite, being able to put away a large dinner and still have room for dessert, not unlike Luke Triton. She often fixated on foods, especially sweets and desserts, for which she seems to have a particular affinity, and often makes unwieldy comparisons between them and the mysteries she solves.



Layton's Mystery Journey: Katrielle and the Millionaires' Conspiracy

Pre-game (Case 10)

About 10 years prior the events of the game, Katrielle's father mysteriously vanished. This lead to her beginning to investigate in order to find him.

Some time prior to opening the Layton Detective Agency, Katrielle encountered Inspector Ercule Hastings at Scotland Yard, who, at the time, was interrogating Ernest Greeves, a student under suspicion of stealing research papers belonging to Gressenheller University professor Dr. Gene Ohm. Disgusted by Hastings' jumping to conclusions and lack of evidence, Kat convinced him to release Ernest and resume the investigation.

Gressenheller being her next stop anyway, Katrielle joined Ernest in returning to the university, offering to prove his innocence -or guilt- "en passant." Once there, her instincts lead her to retrace Ernest's steps that day to the letter, including stopping to smell roses. This lead to her discovering the truth of the case, clearing her new friend's name. In appreciation and affection for Katrielle, Ernest joined her as an unpaid assistant.

Case 01

Soon afterwards, Kat opened the Layton Detective Agency. The agency's slogan, "any mystery solved," lead an amnesiac dog she dubbed Sherl to test her mettle with a puzzle before enlisting her services in uncovering his past. Kat, however, put this on hold in favor of a "more interesting" case: the apparent theft of the hour hand of one face of Big Ben, brought to her attention by Inspector Hastings. Kat, Ernest and Sherl, now working as a team, lead an investigation from the inside of Big Ben to Chancer Lane, the street on which the Layton Detective Agency could be found, where they visited a popular restaurant worked at by a friendly waiter and Lipski's Patisserie - run by Aleks Lipski, brother of clock technician working in Big Ben, Hans Lipski. The team discovered many of the items of furniture and decoration in Lipski's patisserie were made of wafer, and uncovered plans for a wafer clock hand in the waste paper bin in front of the pastry showcase. From her findings in Big Ben and at the patisserie, Kat ultimately deduced that the missing clock hand was not in fact stolen, but was instead melted by the rain - as it was made of wafer. Hans had broken one of the original clock hands whilst working in the tower and so Aleks, his brother, constructed a decoy hand out of wafer so no one would find out about Hans' mistake.

Case 02

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Case 03

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Case 04

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Case 05

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Case 06

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Case 07

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Case 08

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Case 09

On St Godwin's day, a holiday which Ernest explains is celebrated in London during which all the shops are shut and nobody works, as Kat, Ernest and Sherl are ready to go out for the day, Inspector Hastings bursts in.

Case 11

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Case 12

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Layton Mystery Detective Agency: Kat's Mystery-Solving Files

In the anime as connected to the game, her backstory is revealed further, as the mystery behind her birth unravels.

In the "Professor Layton and the Relics Treasure" subseries, it is revealed that a 15 year old Luke Triton was present during her birth on a then-sinking ship, and helped to deliver her, while watching over her dying mother. The woman, Kamilla Azan entrusted the baby to Luke; asking him to explain her situation and how "her husband" was looking for the Hidden Relics to Professor Layton. When the ship later sunk, Katrielle was very briefly cared for by Luke; later Luke returned to London and explained what had happened to the Professor, who took the baby into his own care, as Luke was still pursuing his studies internationally. The professor stated that he would take care of the baby as if she was his own and named her Katrielle Layton.

When she was 10 years old, Katrielle said goodbye to Layton and Luke before they went on a journey to solve the mystery of the Hidden Relics from which they didn't return.

Eleven years later, Rosa comes to the detective agency to explain everything she knows about Layton and Luke's journey. During the tell, Katrielle takes another look at the letter than her father left for her, which is a puzzle for her saying if she isn’t his real daughter, then what is she.

Rosa explains that Layton and Luke went on his journey to figure out the secret of the Relic Stones for Katrielle, for the mystery is so much related to her mother. The last thing Rosa knows is that they found the location where the Relics were hidden originally, but that it was empty now.

After hearing Rosa's tell, Katrielle doesn’t believe that one of her father’s deductions was correct however and believes that Kamilla came back to London so she could obtain a seventh Relics Stone; the professor's assumption was that there are only six of them. With this in mind, she also decides to take on this case and solve it for herself.

Katrielle, ernest and Sherl visit a library first, where Katrielle deduces that the Relics mystery was already solved many years ago. She finds a ledger of all items sold on auctions in London in the past 200 years and notices that all the relic stones were put up on auction periodically starting from 110 years ago meaning that the mystery must’ve been solved around then and the person who solved it wanted to scatter the stones so no one else would discover it.

Katrielle found that someone named Earl Drake Dellendar was the person who purchased the Relic Stones the most and so believes him to be the person who found the Relics. She notes that he expanded the Cranscoll Cathedral in Southampton one hundred and eleven years ago and they head there as the only lead to the relics.

After they get off the boat in Southampton, Katrielle takes a look into the boarding records and is confirmed that her father came to this place eleven years ago. She deduces that the Relics were most likely something fairly large as they were ported to Southampton instead of London, as the city streets in London would've made it hard to discreetly transport something that large. She also deduces that the expansion of Cranscoll cathedral was to create a hiding place for the Relics.

They arrive at the Cathedral, where Katrielle figures out a message her father left behind to let her know he was here, and ventures in. They confront the same priest who captured Layton and Luke eleven years ago. Katrielle argues that the Relics shouldn't have been taken from the cave. The cave's terrain was able to null the harmfull energy the Relics emit, but somewhere else this energy will pollute the surroundings. Since no crops were ever exported from the cathedral's area after the expansion as the cathedral bought up them all, Katrielle reveals to know the Relics are inside the cathedral. The priest commands to capture her but she has the backing of Inspector Britannias who gathered every local police officer in the area. They capture the priest before he can do anything.

Katrielle finds a trapdoor in the cathedral leading to a basement and they go downstairs to see the Relics, which turn out to be a device that induces cryogenic sleep and can therefore be considered as a time machine. Inside coffins of this device, they find both Luke and Layton, asleep. Then Marina Triton, the wife of Luke, appears. She was investigating the Relics all the time, pretending to be one of the priest's men. Now that the priest and his men are arrested, Marina is finally able to open the coffins and set Layton and Luke free. Britannias lets them bring to a nearby hospital to wake up and recover.

In the hospital, Marina tells Katrielle all she knows about Earl Dellendar and the Relics. She tells her that the Earl used the Relics to bring himself and his son to the future. He had ordered he priests of the cathedral to take care of the Relics device for all the years. But eleven years ago something went wrong and the Earl died. Because the organization of the Earl was ordered to annihilate all the priests if the Earl's life would come in danger, the priests had to hide the accident. Therefore, Layton and Luke were used as substitutes to make it look like the Earl was still alive.

Later outside, Katrielle reveals that a third person was using the Relics device, along with Layton and Luke. But this person was revived before their arrival. On the floor before the third coffin, Katrielle found an artificial replica of a Relic Stone. She supposes the stone is a challenge the person left behind for them. For she has an idea of who this person is, namely the so-called "Genius of the Century" Rufus Aldebaran who was a good friend of Earl Dellendar, she, Ernest and Sherl go back to London to visit the estate where Aldebaran used to live.

They have only just arrived when Layton and Luke arrive at the estate as well, and Katrielle finally reunites with her father. Together, they investigate Aldebaran's estate, which points out that Aldebaran was an astronomer, demanding a huge fee for his deductive abilities. Everything indicates Aldebaran himself was asleep in the Relics as well, together with the Earl and his son, but woke up a while before the accident. After solving a few puzzles, they discover Aldebaran wants them to go to Greenwich Observatory.


  • She is 21 years old, as noted in Millionaires' Conspiracy.
  • In the anime, Luke Triton is present during her birth, implying her 21 years of age passed since the end of Unwound Future. This also includes any time passed since Unwound Future ended and before her birth; as well as any time that passed since in the present day of the anime.
  • Katrielle is a name that means "God is my Crown". It is Hebrew in origin, much like that of Layton's. It is regularly spelled Katriel, or Catriel. Also because of this, when the game was first revealed, many initial mistranslations of her name resulted (from news sources as well), including such translations as "Catriel", "Katriel", and even "Catoleil".
  • w:c:yokaiwatch:Katrielle Layton Katrielle and her father appear in the game Yo-Kai Watch: Wibble Wobble as Yo-Kai, with Kat being a Charming tribe Yo-Kai.
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