Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they have a home with their grandfather, and they're about to meet a mysterious mummy!   The Greenfield Museum is holding a special exhibit all about ancient Egypt, and the main attraction is a 4,000-year-old mummy. The Aldens are helping the museum curator set up the exhibit and learning all about life in ancient Egypt. But ever since the mummy arrived, nothing's gone right for the museum or its workers. The longer the Aldens are around the mummy, the more things go wrong. As the children search for the cause of all the bad luck, everything points back to the spooky sarcophagus. Has the museum been struck by the curse of an ancient mummy? The Aldens are about to find out, whether they're ready or not!