The main protagonist of Kingdom of Liars is currently unnamed. All that is known of his background is that he has a sister named Amiel and that he and his sister arrive in Ashbane for him to join the Elk Guard.
He stops the train from having a collision right after everyone aboard is killed. The unnamed protagonist is officially a part of the Elk Guard after speaking with Captain Whelek at headquarters. The protagonist meets Tommy Wilcock while they both investigate a tavern that has burned down, where they find a foreign artifact unharmed among the debris. After taking it to Borynn the Alchemist, and later having it looked at by Shribryn, the protagonist learns that the artifact was specially ordered from a warehouse on the other side of Ashbane. When the protagonist arrives, he finds several dead men outside and a door rigged to explode. Using whatever items the protagonist has on hand, he deactivates the bomb and enters the lab where he finds a Fithling Scientist. The Scientist reveals he was hired by someone to build the weapon that killed the men on the train and that it was designed for a specific target. But his employer betrayed him and killed his henchmen, forcing the Fithling Scientist to lock himself inside his lab. The protagonist arrests him and after he interrogates the Scientist with the help of Warren, the Fithling Scientist reveals who the intended target was...Sir Brandt. However, it was Brandt's brother who was killed aboard the train, not Brandt himself.
The protagonist and the other new member, Vic'eren, are appointed by Whelek to hunt down the assassin. They track the assassin down to City Hall where Sir Brandt is expected to give his speech. While Warren keeps the "snooty bigwigs" occupied indoors, the hero and Vic'eren explore the sewers. They meet two sewer rats, Pikker and Kikker, but are not too friendly with the "abovers". They saw the assassin run through, but require a blue dress for their own purposes before they leak informatino (which the protagonist can get from Courboyn the Merchant). The protagonist and Vic'eren make their way past a door sealed by dark magic and disable a bomb rigged to explode in a hole drilled to the inside of City Hall. However, they are stopped by Butler Sermonde, who demands they shower because they smell of sewer. However, the two restrain Sermonde with shackle-cuffs, and proceed on. The protagonists sees Whelek in the crowd, and warns him the assassin is already in City Hall, causing him to order all the Elk Guard to split up and secure a perimeter. When the protagonist goes up the stairs, he encounters a suspicious waitress who turns out to be the assassin herself. She reveals the weapon she used to kill Brandt's brother concealed inside herself. But before she can shoot Brandt, Vic'eren takes the shot, and the protagonist apprehends the assassin. Though it was never revealed who the assassin really worked for, the protagonist thinks its possible Sir Brandt himself hired her as a publicity stunt.