The story "The Mystery of the Stolen Boxcar" by Gertrude Chandler Warner follows the adventures of four siblings known as the Boxcar Children. In this installment, they stumble upon a mysterious situation involving a stolen boxcar, leading them to uncover clues and solve the mystery. Their teamwork and resourcefulness play a central role as they navigate the challenges presented by the case.

The phrase, "See you day after tomorrow!" reflects the anticipation the children feel as they engage in their adventure. Their enthusiasm and curiosity drive the narrative, showcasing their bond as they work together to resolve the mystery. Ultimately, this story highlights themes of camaraderie, problem-solving, and the excitement of discovery.