The episode begins one night with a diesel engine pulling a passenger train. Suddenly, a steam engine decorated with a skull and crossbones appears out of the tunnel and crashes into the diesel at the crossing.
At Action Headquarters, Meltman tells the Action League he found his original nose. He asks Thundergirl if after he gets it reattached, she'd like to ride in his new sports car. Thundergirl refuses, saying she's busy. The Chief starts the meeting by saying there have been many train crashes on the B.O. Line lately, and they are going undercover to investigate. Before they leave, he asks the League if they have any questions. Meltman has just one; is plastic surgery covered by their health plan?
Moments later, Thundergirl and Meltman ride the diesel engine, which is now pulling a frieght train. Meltman is able to whistle again, as he hasn't been able to since he was melted. Unknown to the League, His Dishonor, the Mayor, is spying on them. He looks through his binoculars and sees Stinky Diver and The Flesh repairing the railroad tracks. The Flesh sings a traditional railroad song and tells Stinky to sing along as they hammer in the nails. The Flesh then accidentally hits Stinky's toe with his hammer. The Mayor says that nothing must interfere with his evil plan, and sets the remote to "Evil Speed", causing the diesel engine to speed up. Thundergirl likes the new speed, as she loves the wind in her hair. She and Meltman duck under a billboard, which accidentally knocks Meltman's nose out of his hand, causing him to scream. The Flesh hears Meltman's scream and tells Stinky that Meltman's in trouble and they have to save him. They climb aboard a handcar and set off to the rescue, but The Mayor sets the switch to a dead end, causing them to land in a washing machine. He then plans to destroy Meltman and Thundergirl, and sends the steam engine with the skull and crossbones to crash into them. Thundergirl tells Meltman they have to leave, but Meltman refuses to leave without his nose. He jumps to the diesel engine as The Mayor prepares to witness the train crash. Meltman reaches the front of the engine and tries to grab his nose, which causes the train to derail. The steam engine crashes into the diesel engine's hopper as the diesel engine crashes into The Mayor.
After the crash, The Chief asks The Mayor why he was causing so many train wrecks. The Mayor, who is wearing a party hat, tells him he did it for the insurance money, so he could throw himself a really big birthday party. The Flesh tells The Mayor that he loves parties, but The Mayor tells him he's not invited. Thundergirl recovers Meltman's nose from the rubble and thinks the train crash killed him. Before she can reveal how she truly feels about him, Meltman rises from the rubble to ask her what she was trying to say. Thundergirl tells Meltman he owes her ten dollars, and Meltman sighs as the episode ends.
- Meltman: "Hey, you guys, look! I found my original nose! Hey, Thundergirl, after I get it reattached, how bout' going for a ride in my new sports car?"
- Thundergirl: "I'd love to. Wait? you mean with you? Sorry, I'm busy."
- The Flesh: "Come on, sing with me! It's a railroad tradition!" (Singing as he and Stinky hammer in the nails) "It's back-breaking work and the pay is low, sweatin' away on the Old B.O.!" (He accidentally hits Stinky's flipper with his hammer)
- Stinky: "Ow! You idiot! You crushed my toe!"
- The Flesh: "Earnin' my pay on the Old B.O.!"
- (Meltman screams as he and Thundergirl go under a billboard, which knocks his nose out of his hand)
- Thundergirl: "Wuss."
- Meltman: "No, no, you don't understand; I dropped my nose!"
- The Chief: "Why'd you do it, Mayor?"
- The Mayor: "For the insurance money, so I could throw myself a really big birthday party!"
- The Flesh: "Goody! I love parties!"
- The Mayor: "You're not invited!"
- Thundergirl (sadly holding Meltman's flattened nose): "Meltman's nose; it's all that's left of him, and I never got a chance to.."
- Meltman (rising from the rubble): "Never got a chance to what, Thundergirl?"
- Thundergirl: "...get back that ten bucks you owe me."
- Meltman (dejected): "Oh."
- Narrator: "The end."
- This episode's title is a pun on the traditional children's song, "I've Been Working On The Railroad".
- This episode marks the first appearances of the Action League and The Mayor.