On a cloudy London night, where the fog mingles with the sounds of the weary city, a hesitant knock comes at the door of the renowned detective Hercule Poirot. A mystery enters, one that will haunt his mind until the very end. A young girl, pale as a shadow, stammers before uttering words that would shake anyone to their core: "I think I've killed someone."

As soon as she makes this shocking confession, she flees, leaving behind a void heavier than her presence, and a mystery that demands to be solved. Who is she? What has she done? Is it the madness of a troubled girl, or a genuine cry of guilt?

Thus opens the doors of "The Third Girl," where nothing is as it seems. An elegant house inhabited by three girls conceals dark secrets behind its walls. Ordinary faces, under Poirot's scrutiny, transform into masks of suspicion, and seemingly innocent relationships reveal themselves as a web of deception and concealment. Every small detail leads to a greater surprise: a fleeting touch, a casual word, a nervous gesture. With each step, it becomes clear that the truth is not simply a murder, but a whole world of psychological conflict, self-destruction, and fear of confronting the past.

Christie demonstrates that true horror lies not in blood or crime alone, but in the enigma of the human psyche where love intersects with fear, guilt with innocence, and reason with madness. "The Third Girl" is a story of faces that conceal secrets, doors that open onto nightmares, and a truth that lurks between the lines. A mysterious crime… perhaps merely an illusion, or a curse waiting to be fulfilled.