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 Aldens are helping out at a rescue ranch for horses. Jessie's favorite is a beautiful horse named Dragon. When Dragon and other horses disappear from the pasture, the Boxcar children must saddle up for a mystery. What's happening to the horses at the Dare To Dream Ranch?