M
Mary Roberts Rinehart
A crime writer often called "the American Agatha Christie" (Wikipedia).
The Man in Lower Ten
Attorney Lawrence Blakely's train journey takes a dangerous turn when he finds himself embroiled in a murder investigation. Tasked with delivering crucial documents for a criminal case, Blakely becomes a suspect and a target as someone relentlessly pursues him and his papers. This classic mystery by Mary Roberts Rinehart promises a suspenseful tale of intrigue and unexpected twists.