Martina is feeling a bit low: her parents pay more attention to her little brother, who is teething. One day, annoyed because her brother has torn a soft toy, she decides to go to the world of monsters to play with her friend Anitram; her brother Marc secretly follows her. But Marc begins to play with Cram, Anitram's little brother, and the two get lost. Martina and Anitram search for them, and end up in The Land of Lost Socks, where the king sets them a series of riddles they have to solve to find their brothers. Together they defeat the evil king and Martina discovers that being an older sister isn't so bad after all.