Karen, Ken, Sally and Andrew haven't a care in the world as they put all their energies into learning to ride major Phillip's beautiful horses in the summer of 1977. Little do they know that a casual visit to their old friend Jimmy Burroughs will once more plunge them into intrigue and mystery. Jimmy shows them an old and mysterious trick box that has been in his family for generations, and sets them on a path of discovery. Who was Riddler Jack? What's the story behind the box? At every turn they find that they are not alone. The brooding professor Silas Hawkwing dogs their steps. What does he want? Are they imagining the hint of menace he seems to carry about. The four find themselves delving deep into the past and uncovering a tale of highwaymen, family feuds and rough justice. Can they solve the clues and follow the trail to the end?