One warm night four children stood in front of a bakery. No one knew them. No one knew where they had come from.

Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they ahve a home with their grandfather, and they're vacationing on a beautiful island known for its sandy beaches--and its wild ponies.

Henry, Jessie, Violet, and Benny have promised Grandfather a vacation from mysteries during their island visit. But the promise proves hard to keep when things start to go missing. Then an old fisherman tells Benny of the island's ghost horse, and late that very night Benny sees a nysterious stallion galloping down the beach. Could the ghost horse have something to do with the disappearances? Or is there something--or someone--else wandering the misty dunes at night? Vacationn or not, the Boxcar Children are determined to solve the mystery!