Modo, who first made his appearance in The Hunchback Assignments, is a young, disfigured spy trained to be the ultimate secret agent. Not only is Modo brilliant and strong, but he also has a special ability: he can temporarily take on the appearance of other people. While on holiday, Modo and fellow spy Octavia Milkweed find themselves in Ember's End. Created by the slightly mad scientific genius Dr. Ebenezer Ember, this is no ordinary wild-west town. It is surrounded by an energy field that prevents gunpowder from firing, and messages are sent via pneumatic tubes. There are also rumors that before Dr. Ember died, he built a weapon so powerful it could end all wars. With the local sheriff recently deceased, the two travelers are suddenly put in charge of Ember's End law enforcement.
Joe and his friend Skip are enjoying the thrill of the Big Dip, a famous rollercoaster, until they learn the old man in front of them has been shot. The old man mutters with his dying breath something about getting a Margaret Rose to the police. Joe leaves the crime scene to get on with his life. But someone is desperate for the Margaret Rose and thinks Joe has it. When his sister is kidnapped, Joe is in a race against time to solve the puzzle.
Zack Freedman has complete control and feels a sense of calm on the high wire. If only he could say the same about the rest of his life. His fellow youth circus performer and roommate, Cubby, hates him, and his aunt dumps a yappy, excitable dog on him. When a necklace is stolen during a circus performance and the victim of the theft threatens to shut down the circus, Zack is desperate to solve the mystery so he can keep his place on the wire.
While volunteering at the local zoo, Robyn, Nick and Trevor learn that grizzly bears are being poached and their gall bladders removed for use in alternative medicine. Always ready to solve a mystery, the kids set out to find the poachers. Bear is not only big game, they learn, but big money to poachers. The stakes are high and the suspects many, as the kids head into their most dangerous adventure yet.
When Trevor, Nick and Robyn visit the Royal Tyrrell Museum, Robyn is inspired to raise funds for a dinosaur dig that will close soon if it doesn't find funding. The kids are caught up in another mystery when a chain of suspicious events, including the disappearance of important fossils and a fraudulent discovery at the dig, leads them to wonder what's going on. Is the new visiting scientist behind the fraud, or did Robyn's enthusiasm to save the dig lead her astray?
Trevor, Nick and Robyn are ready to solve another mystery. When bobsledder Josh Gantz is accused of deliberately injuring a fellow competitor, he runs the risk of being thrown out of the sport -- right before the World Cup. Courtney Gantz asks Trevor, Nick and Robyn to help clear her brother's name. Can they find out who framed Josh? What is the meaning of the strange coded messages they keep finding around Olympic Park? Who eats orange bananas, anyway? The kids must unearth the clues in a race against time, before Josh's championship dreams end up on ice.