Christina, Grant, Mimi, and Papa find themselves in the middle of a mystery in Death Valley, California. There's Aunt Erin, a creepy castle in the middle of nowhere, a ghost (or not?), temperatures hotter than a Fourth of July firecracker, and more!

Mimi, Papa, Christina, and Grant make an emergency landing on Diamond Shoals off the North Carolina coast and encounter a mysterious light on the beach.

Christina, Grant, Alexis, and Griffin try to locate the Wright Brother's historic plane, which has been stolen on the eve of the 110th anniversary of the brothers' first flight.

Scientist Artemis Masters travels with his children Curie and Nick to the Adirondacks where he has been hired by local resort owners to develop an early warning system for snowstorms, but when he becomes ill, Curie and Nick take over managing the experiment while trying to figure out why their hosts are trying to sabotage their efforts.

Christina, Grant, Raven, and Hunter arrive in north Alaska for the Iditarod Trail dogsled race just in time to pursue a runaway team with a renegade musher.

When they travel by train across America, Christina, Grant, Mimi, and Papa find themselves facing mysterious mishaps, spooky surprises, and treacherous tunnels.