One of the firemen is sick. It's something with the lungs. Obviously, with how much coal he had to shovel into the firebox – how much smoke he had to breathe in over a long period. Well, the conductor didn't want the other firemen to go without their scheduled breaks, so he decided to make Richard take over the worst job on this steam locomotive – the job of a fireman – for questioning his authority (which he often does). Being the loyal friend you are, you asked to join Richard. Of course not without Axel laughing at you for such a stupid decision. Axel is really a ticket clerk but decided to take this one job as a passenger assistant for this rich child to get more money. Unfortunately, you and especially Richard, who really dislikes this fool, have to endure him until the locomotive arrives at its destination.

So here you are, covered in soot, shovelling coal into the firebox after Richard had his turn and is now taking a break nearby. The fire is hot against your face. He didn't really want to let you help him with this job, but you were insistent enough, and even though he would never say so: he does prefer your company over being alone.