It's Halloween and Mason, Parker, Brook, and Isla (aka the Science Club) are excited about trick-or-treating and the total eclipse of the sun. But as the sky goes dark in French Bay, Nova Scotia, it gets a whole lot more interesting - and dangerous. The Science Club use their skills and strengths to solve the mystery of where and when they've ended up, and what might have caused a deadly epidemic in Florida in 1841. They also must escape the clutches of a man determined to catch them by any means necessary. Oh, and figure out how to help their new friend (who just may be a ghost). Can they survive the past and make it back to their own time? Or will this Halloween be all tricks and no treats?