 Ernie, Tod, and Sandy Devlin are siblings whose parents have been deceased for quite some time, and are part of a motorcycle daredevil act with a traveling circus. Ernie is the oldest sibling and is the main attraction to the act. Tod, who is about a year younger, is the main mechanic and driver of their RV. While Sandy, a high school freshman, is assistant mechanic who also occasionally joins Ernie on the back of his bike after one of his stunts, and also is learning a lot about life from her older brothers. It also seems that in every place the circus performs, a mystery is in need of solving, and it ends up being up to the Devlins to solve it.