F&F play a trick on the fishing Lupo and forget about their boat, which drifts off. With all the tricks they can finally board it - but then a waterfall comes. While fishing Lupinchen comes across a mysterious ring - and a little later a prince appears who wants to marry her (and is very interested in the ring). F&F are suspicious. The boys have built a tree house, but want to keep it to themselves. Lupinchen first has to pass a test of courage to be accepted into the club - and she shows them the way. Pip and Pep want to help garbage man Lizzer and terrorize the disposing neighborhood - and their father. He only converts when he hears that garbage can also be sold.