depends which stage
go on the top of the train
You can get up via the open hatch in the baggage car.
under the top box on top of his dresser
When you get to the fair on Mystery Train Island, you have to find the girl from Paris. The one who stole the invention. She will say help to the guards and you have to stay on top of the buildings to stay out of reach. When you do that and get to the next part, do the same thing, except with statues. Then you have to climb the wheel and capture her. I assumed you were talking about Poptropica. If you were not, sorry.
1. Early Poptropica 2. Time Tangled 3. Wimpy Wonderland 4. S.O.S Island 5. 24 Carrot Island 6. Ghost Story 7. Mystery Train 8. Reality TV 9. Big Nate 10.Wild West Island
You click on the map (it is in the right hand side corner at the top), and at the bottom left hand side there is a blue circle that says Restart Island. Click on it and you will restart the island.(Notice that it is not the map of all the islands but just the island map of Mystery Train.)
Put the suitcases in order from shortest to tallest, then put the board on top and your Poptropican will push the trunk onto the train.
Once Tesla is taken out and guarded, you can go into the luggage room and there is a door at the top that opens. You can go out to reach the coal car, but there are hazards (tunnels, mail sacks).
You go in the luggage car and the hatch on top is open. Go on top.
he goes on top of the train and you follow him on top of it.Then he falls through some bricks and you go through the bricks he fell through.you don't really catch him over all because the bricks he fell through leads to a water tank and you use his lock picks to free him from the tank.After you save him he vaishes.
Jump
Big Nate Island on the Poptropica map is the 9th from the top.