Snowbound Mystery - Gertrude Chandler Warner

When a terrible snowstorm hits the area, the Boxcar Children are trapped. To make matters worse, there's something very suspicious about their cabin. What are all those strange markings on the closet door? And what are all those strange noises the Boxcar Chldren hear in the night? A freak snowstorm isolates the Aldens in a mountain cabin where they discover a coded message.