"Marie-Grace can't wait to begin her journey up the Mississippi River with her father. The steamboat they're traveling on is the biggest and fanciest boat Marie-Grace has ever seen. It's crowded with all sorts of interesting passengers, including Wilhelmina Newman, a girl her age. Wilhelmina is traveling alone, and she's carrying a secret in one of her trunks--clues to hidden Gold Rush treasure. Marie-Grace and Wilhelmina have to unravel the clues...

In 1860, eleven-year-old Becky Thatcher, new to St. Petersburg, Missouri, joins the boys at school in a bet to steal from the Widow Douglas in hopes of fulfilling a promise to have adventures that she made her brother Jon before he died.