Gramps gets a good bargain on an apparently perfect bay mare for Lily, but because the horse is named Beware he suspects that there may be something wrong with her.
Just after Mandy witnesses a ghostly young horse disappear in the fog, she encounters a girl who has been visited by her own deceased foal, named Curiosity, leaving Mandy to wonder about this coincidental occurrence.
When substitute middle-school history teacher Rush Revere takes his students back in time to eighteenth-century Massachusetts, they witness the Battle of Lexington and learn about the Declaration of Independence.