Pat Spain goes to British Columbia in search of Cadborasaurus, or "Caddy" as it is fondly known. He talks to local witnesses who claim to have seen the monster, hangs out with local fishermen, and spots local whales. He speculates that some Caddy sightings could be humpbacks surfacing in unison, or perhaps porpoises. He also pokes around in the Woods Hole Institute's freezer, checking out their specimens, and talks to some First Nations folks about native legends (Caddy has a long history). He also looks at possible historical and current candidates, including the elusive oarfish. Then he goes diving into the deep (in a submersible), where he sees strange things, like a giant jellyfish. In the deep, Pat believes, an unknown sea monster like Caddy could exist.