Calvin asks Hobbes to look at his newest invention. It's a box, sitting open on its side. Hobbes asks if that isn't Calvin's transmogrifier. Calvin says that it was, but he made some modifications. It's now a duplicator. It combines the technologies of the transmogrifier and a photocopier. Instead of a reproduction on paper, you get a real duplicate. Hobbes asks if their financial worries are now over. Calvin tells him counterfeiting is just one of its many uses around the home.

Hobbes asks if Calvin has tested his duplicator yet. Calvin is ready to. Hobbes asks what they should duplicate first. Calvin volunteers himself. He says Mom wants him to clean his room, so he can duplicate himself and let the duplicate do the work. Hobbes says he can picture the looks on his parents' faces when they find out they've suddenly had twins. Calvin thinks he can make a whole baseball team this summer.

Calvin tells Hobbes to push the button to duplicate him. Hobbes isn't so sure he should. Calvin criticizes Hobbes as a doubting Thomas getting in the way of scientific advancement with their stupid ethical questions. Hobbes says he'd hate to be accused of inhibiting scientific progress, so he pushes the button. BOINK! Hobbes asks if scientific progress goes boink. Inside the box, Calvin says that it worked and he's a genius. Another voice calls Calvin a liar and says he invented it.

Calvin introduces his duplicate. Hobbes isn't sure he's ready for this. Calvin tells his duplicate that he and Hobbes are going out to play. The duplicate will clean Calvin's room and do his homework. The duplicate doesn't like that. He runs off, telling Calvin to find another sucker to do his dirty work. Hobbes comments on how he is a duplicate of Calvin, all right. Calvin asks what he means. He says the duplicate is a total jerk.

The duplicate walks by Mom dressed to go outside. Mom asks if he cleaned his room like she asked him to. The duplicate tells her that he's going outside and that Calvin can clean his own room. Mom doesn't want any nonsense and tells him to go upstairs. As he walks away, he says he's Calvin's duplicate. Calvin is upstairs. Mom gets angry and tells him to go to his room. The duplicate says she's a crabby lady. He asks if she's Calvin's cruel governess.

Calvin and Hobbes leave the bedroom to look for the duplicate. Mom is putting a coat on the duplicate, who keeps telling Mom that he's not Calvin. He says Calvin is in his bedroom. Mom opens the bedroom door and shows there is no one there. She tells him no more games and to clean his room. Calvin is getting his coat on to check outside for the duplicate. Hobbes says they better hurry. He hears Mom coming down the stairs.

Mom sees Calvin outside. She asks if she didn't just send him to clean his room. Calvin replies no. Mom brings him inside and says she did tell him to clean the room. She says she's losing patience for this game. Calvin tells Hobbes she must have seen his duplicate. They go to find the duplicate before he can cause any more trouble. In the bedroom, another duplicate walks out of the duplicator. Number two introduces himself to number three.

Calvin and Hobbes run up the stairs. Calvin says Mom must have sent his duplicate upstairs. Hobbes says this is turning into a mess. Calvin complains that the duplicate gets in trouble, but he gets the blame. They're horrified as they open the bedroom door. Hobbes says Calvin's duplicator is a big success as he looks at five duplicate Calvins. One of them says the duplicator burned out after the fifth one.

Calvin is horrified to see his duplicate made duplicates. Calvin wonders what he should do. Hobbes suggests telling Mom to put out extra table settings. Calvin tells the duplicates they have to stay in the room and keep quiet. None of the duplicates want to do that. Calvin says that since he's the original, they have to do what he says. The duplicates suggest putting it to a vote.

One of the duplicates is going to get some cookies. One of them is going outside. Another one wonders what's on TV. Calvin tells them Mom will see them. One of the duplicates says that as long as they split up, every time Mom sees one of them, she'll think they're Calvin. The duplicates laugh and walk off. Calvin calls them a bunch of devious little stinkers. He wonders where they learned to misbehave that way. Hobbes thinks they should check into a hotel until this is over.

Mom tells Calvin not to eat cookies before dinner. She asks if he cleaned his room yet. The reply is that he's not Calvin, he's a duplicate. Mom storms off saying "some days that kid of mine". She sees Calvin in the living room watching TV. She asks what he's doing in there. The reply is "are you taking a survey".

Dad gets home, and Calvin says hi. Dad replies, and another Calvin comes by to say hi. Dad says that he already told him hi. Another Calvin says hi, and Dad tells him to knock it off. Mom tells Dad that he should have a talk with Calvin. He's been driving her crazy.

Calvin tells the duplicates that since he doesn't know how to get rid of them, they might as well cooperate. He says they can divide up the school week, since there are enough duplicates. There's one for each day. Calvin says if the rest of them lay low, they can take turns going to school, and no one will be the wiser. Calvin ends with the question of who will get the bed. The duplicates offer to fight him for it.

Susie says hi to Calvin. The reply is that he's duplicate number two. Susie asks what he's talking about. He explains that they drew straws, and it's his day to go to school. They're taking turns. Susie says Calvin's so weird, she isn't going to talk to him. He says he's not Calvin. Susie wishes she lived someplace where she went to a normal bus stop. He asks if she'll help him find Calvin's locker.

Miss Wormwood asks Calvin to demonstrate the homework problem that was assigned. Calvin says he wasn't there yesterday. Miss Wormwood says he was present. The explanation is that he is duplicate number five. Duplicate number two was at school yesterday. They are taking turns. Number two will be back next week, so she can ask him to do the problem then. In the principal's office, Calvin says he doesn't see what's so hard about this.

Number four comes in the bedroom. He tells the others it's okay to come out. They ask how school went. He tells them he was sent to the principal's office, just like numbers two and five did. Calvin says not even he got sent to the principal's office every day. He says they're making him look bad. One of the duplicates says that if Calvin doesn't like their performance, he can go to school himself. Calvin says they shouldn't jump to conclusions. All he's saying is there is room for improvement.

Calvin tells Hobbes they need to get rid of the duplicates. All they do is get him in trouble. Calvin says everyone thinks he's doing all these rotten things, when it's really a duplicate. He's being framed by his own doubles. A bunch of duplicates run past Calvin, saying "run" and "hide". Hobbes says it appears Calvin has perpetrated another crime. Calvin complains that the worst part is that he doesn't even have the fun of doing the stuff he's getting blamed for.

Calvin asks the duplicates what they've done now. They tell him to hide, because Mom is on the warpath. All the duplicates hide under the duplicator box when Mom comes in. Calvin smiles and tries to look innocent while Mom asks him to explain his behavior. From under the box, Calvin hears whispered a request to have a bigger allowance. Five times bigger. Calvin asks if he can get back to her on that issue.

Calvin is depressed that Mom read him the riot act. Hobbes whispers a suggestion to Calvin, who smiles. From under the box, voices ask if Mom has left, if the coast is clear, and whether they can come out. Hobbes says Mom is coming back again. Calvin tells the duplicates to be quiet. Calvin calls Hobbes a genius, as Calvin changes the wording on the box from duplicator to transmogrifier.

Calvin says so long to the duplicates. From under the box, they start to say they're not going anywhere. Calvin turns on the transmogrifier. ZAP! Hobbes asks what he changed them into. Calvin tells him worms. He says he didn't want them to be unhappy.

Calvin tells Mom he won't be getting into trouble anymore. Calvin again explains that he made duplicates of himself, and it was the duplicates who were bad. Calvin shows her that he transmogrified them. He holds his hands open, showing the worms. Mom yells for him not to carry worms through the house. She sends him outside. Calvin digs a hole to put the worms in. He tells them they got him in trouble one last time. He hopes they're happy. The worms ask if he doesn't want to put them on Dad's dinner plate tonight before they go.

Calvin tells Hobbes that they learned a valuable lesson from this duplicating mess. Hobbes asks what that lesson is. Calvin thinks about it, but can't come up with anything. As they walk off, Calvin says "So we didn't learn any big lesson. Sue me". Hobbes replies "Live and don't learn. That's us".