The Mattigan kids don't believe in things that go bump in the night.
After all, their dad is famous for proving such things are impossible.
But, when their long-lost Grandpa Joe shows up with his Mysterious
Monsters journal, begging for help, the siblings find themselves drawn
into a search for Bigfoot.
Along the way, they'll have to deal with meddling babysitters,
suspicious psychics, a YouTube disaster, and their furious father. To
solve this mystery, Maddie, Max, and Theo must rethink what's
possible--and make lots of peanut butter and banana sandwiches.