Ten-year-old Toni is a little scatterbrained, so his parents warn him to take extra good care of his little sister Rita on their first solo train trip to their grandmother in Bamsdorf. But of course Toni doesn't pay attention and gets off at the wrong station, leaving Rita behind in the train. And this is only the beginning of a adventure-filled journey for the siblings.

The story continues in the sequel Adventure in Bamsdorf.