The Dark Ruby Raven or When the Circus Comes to Town‪.‬

When Amy Hayden was whisked away from her job at the Casino she doubted she would ever be able to return, but when a close friend is framed for murder she convinces The Historian to return to help her clear her friend's name. Unfortunately the key to clearing her friend lies in the distant past in a nearby boomtown, where her great grandmother is the local schoolteacher.