The Bridge Trolls from the great undercity of Venice are in turmoil. A dire warning has been delivered from the troll witch that unless the trolls can solve the riddles in her prophesy by the turn of the next moon, the city will sink beneath the lagoon. The grand troll council dispatches forth two young trolls on a mission against time to save the Bridge Trolls' ancient home. Using powerful Vulco-boards to travel, Crankio and Nozio soon team up with Magma, a bossy Bog Troll, and Vespa, a bright little Mountain Troll and the four of them head off on a great adventure.