The Saddle Club girls travel to England where they participate in a competition and try to solve an ancient mystery about a duke who reportedly buried treasure under the stall of his spirited stallion that later died in a fire.
When Stevie Lake gets hurt and can't ride for the entire summer, the other members of the Saddle Club promise not to ride until she gets better. They each have to find a different way to spend their summers.
When Joey Dutton moves away and a new neighbor moves in, May and Jasmine try to find out why lights flicker on and off at night and what is making strange noises in the stable.
When Veronica arranges for the Saddle Club to be stuck at the stables taking care of her horse the night of the Willow Creek Junior High spring dance, the three friends find a way to go to the dance and take Veronica's horse with them.