And once again, the two reluctant teenaged detectives are thrown into the middle of a weird mystery. When a Hollywood studio chooses Riverbend as the location for their new western, Pepper McKenzie decides to try out for a role, and she drags her best friend, Salt, along. But it soon becomes clear that this is no normal movie shoot. The producer and his assistant act more like gangsters than businessmen. And the stars appear to be hypnotized—like zombies, or robots! Could this have something to do with the weird machine Salt spotted at film headquarters?

When Pepper goes missing, Salt is forced to recruit little brother Hal and his buddies to help. Pepper finally does turn up, but she's not quite herself. Before long, the friends have uncovered a devious plot—one that threatens the entire town of Riverbend. Will they be able to stop it in time to save the day?