When Carole Hanson learns that the newly elected president of a Middle Eastern country will be visiting Washington with his horse-crazy daughter, it seems only natural to write the girl a letter inviting her to come for a ride at Pine Hollow. Carole thinks she might get a reply with an interesting stamp on it. Instead of a stamp, however, Carole gets men with dark suits and sunglasses who walk around Pine Hollow talking into their lapels, looking for spies in the hayloft, and asking for security clearance for horses. Isn't this a little extreme? Especially since the four girls only wanted to go on a trail ride!

But when a real spy turns up at Pine Hollow, The Saddle Club rides to the rescue to protect national horse safety!