Pekka receives a package from his Uncle Remu. Inside is a metal detector needed for treasure hunting. However, Pekka only finds tin cans and rusty nails. But then Uncle Remu invites him on a trip to Japan. Pekka must take the metal detector with him because Uncle Remu wants to find a famous samurai sword made of an indestructible metal there. He needs it for his latest invention: a poop engine that runs on gas derived from farts instead of gasoline. But once again, the shady Captain Hahab crosses Pekka's path, and another exciting adventure full of wit and humor begins.