Mysteries abound at Saskatchewan's Government House, and Sam and J.J. are once again tasked with solving them – before it's too late.

Things aren't as they appear at Government House, as Sam and J.J. discover on a field trip when they find themselves at the turn of the 20th century discussing mushroom growth with George Watt, the gardener of the property. In an attempt to uncover what happened, the girls find themselves back in the present, face-to-face with the ghost of a woman who simply mouths the word "watch" to them.

Who is this mysterious woman, and what does she want? In order to solve the mystery, Sam and J.J. must navigate the grounds of Government House (both past and present). And with only the faintest idea of how to return to their time, their forays into the past become dangerous. Can they figure out what the ghosts wants before they are stuck in the past for good?