Penny Preston and the Silver Scepter

When Penny solves the riddle of an unbreakable knot in time, she unwittingly releases two time-travelers from the distant past into Piper Falls. The town is plagued by a series of baffling events related to the appearance of a strange elf-like creature. Penny's science teacher and mentor, Mr. Myrdin, recognizes him as the Coch Coblyn. An evil spirit from Celtic myth with a penchant for igniting city destroying fires.
Compounding the mystery is the discovery of a prehistoric scepter, made of impossibly pure silver that's intertwined with Seneca creation myth and Master Poe's past. The silver scepter draws the sole survivor from the ancient civilization that created it to Piper Falls. After traveling forward thousands of years in time, he plans to take the scepter back to his own time and save his people from the cataclysm that destroyed them.
Stumped by the escalating pranks of the Coch Coblyn, the Deputy Sheriff contacts his good friend, Darin Kolchak, a paranormal investigator. Kolchak answers the call by bringing the latest in ghost-hunting technology to town in his refurbished U-haul. Kolchak's methods may not be conventional, but they lead him dangerously close to the truth. Penny and her friends race to unravel the secrets of the artifact, dodge detection, and prevent either of the new arrivals from using it to return to power.