"Now don't change history while I'm gone," Mr. B had said before leaving Hannah and Nick to lock the trunk in the classroom closet. Despite Hannah's pledge to comply, a trickle of beach sand and a slosh of seawater turn into a flood tide after she lifts the lid. The siblings, along with their friend Jackie, find themselves in a wooden canoe off the seventeenth-century Texas coast--with a gale approaching and nothing to get them home but a magic ring...