Mr. Krabs needs a recipe that is in a locked box. Mr. Krabs gives SpongeBob the key to the box. SpongeBob and Patrick will get the recipe. They take a train. Plankton is on the train because he wants the key. SpongeBob and Patrick are very hungry. They go to the dining car. SpongeBob and Patrick meet a nanny and her baby. SpongeBob meets a porter. The porter does not like SpongeBob. He pushes SpongeBob off his seat! SpongeBob and Patrick leave the dining car. They want to hide the key. The key is gone and SpongeBob cannot find it! SpongeBob sees Plankton and thinks Plankton stole the key. Patrick checks Plankton and sees that he does not have the key. Patrick lets Plankton go. SpongeBob asks Patrick to call the cops. Patrick shouts for the cops. When the cops arrive, SpongeBob tells them about the missing key. SpongeBob points to the baby. SpongeBob thinks the baby has the key. He then points to the nanny and thinks she may also have the key. SpongeBob holds the baby. The police chief searches the baby. He finds a stolen jewel! The nanny opens her coat. She is not a nanny. She is two brothers! SpongeBob has found the Jewel Triplets Gang! But he has not found the missing key. SpongeBob thinks the porter stole the key. Plankton wants the key. He jumps on the porter. A policeman shakes the porter. A stapler, a hammer, and an anvil fall out! A mask falls off the porter. He is really a ham sandwiches thief! But SpongeBob still has not found the key. Wait, Patrick has the key! He gives SpongeBob the key. SpongeBob and Patrick solve the mystery! Now they can get the recipe. Plankton is right behind them.