Twins Domingo and Carmen Rivera are ready for the big Camp Rivals Race, when the four camps compete in an annual cross-country running competition, but this year there are problems: in the boys' race there is a pile-up, and Andy, Domingo's old friend, manages to prevent him from winning--but when Andy sends a text warning Carmen to watch out in the girls' race the twins become convinced that some of the other kids are cheating by working together to sabotage rival runners.