Pettersson und Findus wollen auf den Flohmarkt, finden aber eine Schatzkarte. Um Mitternacht schleichen sie auf das Feld des Nachbarn, um den Schatz auszugraben.
Pettson and Findus are cleaning out the attic looking for old things they can give Henrik for the flea market. Findus comes across a wonderful ‘ship-in-a-bottle’ that he definitely wants to keep. Henrik arrives to take away Pettson’s unwanted items and in the rush of getting everything ready Pettson accidentally puts the ‘ship-in-a-bottle’ in the box to give Henrik.