Next stop on the Cheapo European Tour, Denmark, and it seems there is something rotten in Denmark as the kids run into the ghost of Hamlet at the Castle Hotel Hamlet they are staying in. The ghost wants to let the kids know something though: "Beware, the Briny Boo!" / In the Greek islands, the kids head for Cyclops Island, to find the legendary Mask of Medusa with Professor Mikos. But it seems that Thaddeus Blimp, a master villain, wants the mask too, and he plans to turn all the world leaders and his enemies, including Scooby, to stone.