Trixie Belden and the Mystery on the Mississippi

Plot

The Bob-Whites head to St. Louis with Mr. Wheeler. Dan gets to go! But Diana isn't along for this trip. Anyhow, Trixie finds a briefcase in her hotel room and the owner angrily takes it back. Suspicious after finding some crumpled up papers it the waste basket, Trixie saves them for further examination. Soon, the Bob-whites are being followed and menaced, even as they cruise down the Mississippi.