Every summer, Karlchen, Mama, and Papa go on vacation. They prefer to travel by train. This time, Karlchen is allowed to bring his best friend Monika along. He wants to show her the locomotive, which is at the very front. To get there, they have to pass through five carriages and walk by the dining car filled with sweets. That's already quite a challenge; at the bike compartment, Karlchen needs to take a break first. When he wakes up, suddenly a strange man is sitting next to him and Monika, and the wallet is gone too! Before Karlchen can start looking for the thief, he first needs to go to the bathroom. When he comes back, the conductor and Monika are already standing in front of him with the wallet. Luckily, nothing gets lost on the train!.