The Alden children investigate various mix-ups at a zoo run by their grandfather's friend in an effort to save it not only from pranksters but also from the town council.
When their grandfather arranges for them to spend two week at Sunny Oaks, the four Alden children enjoy settling into the routines of farm life but become suspicious about a mysterious horse locked in the stables.
The Alden children search for buried treasure on Blizzard Mountain, but a mysterious rival treasure hunter is determined to chase them off the mountain.
Henry, Jessie, Violet, and Benny are given the opportunity to be extras in a movie about the Alamo, but they are called upon to use their sleuthing skills when Claire, the star of the film, is implicated in the theft of a valuable ring.
While visiting the seaport town of Ragged Cove, Massachusetts, the Alden children find the ship's log of the Flying Cloud, shipwrecked in 1869, supposedly during a mutiny.