Thirteen-year-old Spencer Herold and his friends Maddy, Babu and Duber Dave are always looking for adventure. They even have a club for it: the Lake Union Adventurers. For the most part, though, their adventures are fairly tame. That's about to change. Then, the city of Seattle is engulfed by horrific weather, caused by a maladjusted Romanian count seeking revenge. Using a handwritten book given to his late grandfather during World War II, Spencer and the Lake Union Adventurers begin to unravel mysteries from the past, and a long history of trickery, betrayal and deceit is revealed. With time running out and the city on the brink of destruction, Spencer and his friends set out to foil the evildoer's plans. As they battle natural disasters and unscrupulous villains, Spencer realizes that his own family is the madman's target.