When professional typist Letitia Glover is desperate to learn more about the fate of her twin sister Flossie, Enola enlists the help of her brother Sherlock and her friend Tewky to investigate Flossie's husband, the sudden death of his first wife, and the mysterious appearance of a black barouche.

"Cuando la señorita Letitia Glover acude a Sherlock para pedirle que averigüe qué ocurrió con su hermana gemela, Enola es quien la recibe. Al parecer--según dice el breve mensaje que recibió--murió su hermana Felicity, casada con el conde de Dunhench. Pero Letitia está convencida de que eso no es cierto: si su hermana hubiera fallecido, lo habría sabido, lo habría sentido en su interior. El mensaje del conde es sospechosamente vago y el certificado de defunción, más dudoso todavía. Solo hay una vía de investigaciones posible: infiltrarse en los dominios del conde. O, al menos, así lo decide Enola, pese a las protestas de su hermano. Pronto descubre que Felicity no es la única de las esposas del conde que ha fallecido súbitamente. El destino de la desaparecida va unido al de un misterioso carruaje negro que llegó a la mansión en mitad de la noche" -- Enola Holmes returns in her first adventure after the success of the Netflix movie, which has taken her back to the top of the sales charts. Enola Holmes is the sister of Sherlock and Mycroft. And just like them, she possesses intelligence, skills and detective inclinations. When Miss Letitia Glover, an emancipated woman, comes to Sherlock asking him to find out what has happened to her twin sister, it is Enola who greets her. Apparently, and according to the brief message she has received from her, her sister Felicity, married to the Earl of Dunhench, has died. But Letitia Glover is convinced that this is not true: if her sister had died, she would have known it, she would have felt it inside her.