The Mystery at the Crooked House — Gertrude Chandler Warner

One warm night four children stood in front of a bakery. No one knew them. No one knew where they had come from.

Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they have a home with their grandfather, and they are visiting the Crooked House, Mrs. McGregor's childhood home in the snowy countryside.

When Mrs. McGregor, the Aldens' housekeeper, learns that she cannot afford to keep the Crooked House, the Aldens want to help. Mrs. McGregor tells them that ever since she was a little girl, there has been an unsolved riddle about the house. And solving the riddle could lead to a treasure! Could the treasure save the Crooked House? Can the Boxcar Children find it in time?