Hugo is a young Sasquatch. Boone is a young boy. After an unlikely encounter, they've become an even unlikelier pair of best friends.

After saving up his Monster Card wrappers, Hugo sends away for a special prize in the mail - a Monster Detector! Using the watchlike device, Hugo quickly spots a monster right in his own cavern. Spooked, Hugo heads to school and finds yet another surprise - his friend Boone!

Boone announces he wants to go to Sasquatch school, but no human has ever gone before, and not everyone is as happy about it as Hugo. Boone's first day of school gets off to a rocky start, but Hugo doesn't have much time to worry before he makes another monster sighting and takes off after the creature.

What follows are even more surprises, ones that have Hugo and Boone rethinking what it really means to be a "monster."