For the episode adaption, please go to "The Sorcery Of Maltrochu (episode)".
The story begins with a prologue concerning a brave knight named Thierry, who wished to marry Genoveva, a wealthy lord's daughter with whom he was in love, but his rival the evil Baron of Maltrochu also wanted to marry her, though just for her father's riches. Since Genoveva loved Thierry, he had to be dealt with, so the Baron invited the knight to a banquet, serving him wine mixed with a magic potion purchased earlier from an alchemist. The unsuspecting Thierry drank it...
At The King's castle, Peewit has been experimenting with alchemy for several days, not stopping even to eat(!). One day, he shows as a result a philosopher's stone... that turns gold into lead. Since Peewit used the King's crown for his demonstration, his angry monarch orders him to work overtime until the crown is paid for.
Days later, the King prepares to go on a hunting trip - without Peewit, but the artful jester persuades him to change his mind with a show of fake tears. During the trip however, Peewit encounters a dog which scares him when it talks to him like a human being. In his fright, Peewit in turn frightens the forest animals the King was targeting into running away, ruining the hunt. Peewit blurts it out to everybody how the dog actually talked to him, but when he tries to get it to speak again it just barks, so as a result nobody takes his claims seriously. Johan decides they cannot leave the dog alone in the forest, and brings it into the castle.
Later, while Johan and Peewit play chess, they hear the dog talking in its sleep. Realizing Peewit was right all along, Johan wakes the dog up and asks for an explanation. The dog reveals he is Thierry, transformed into a dog by the magic potion slipped him by Maltrochu who, upon discovering that his rival can still talk, tried to lock him up, but he escaped. Thierry further explains that when he ran into Peewit in the forest, he initially spoke on impulse, but then fearing the other people in the hunt would burn him for a witch, he chose not to talk to them. Peewit offers to make him an antidote, but Johan, not trusting his friend's alchemy, decides to go seek for the formula in Maltrochu's castle.
Johan and Peewit leave Thierry at an inn and then go to the castle, where they tell Maltrochu they are on a mission for one of the King's nephews to persuade Genoveva to marry him. Maltrochu tries to dissuade them from their mission by throwing them a banquet, during which Peewit pretends to be pining for a maid engaged to another man. Falling for the ruse, Maltrochu offers him and Johan a deal - he would send them along with his servant Hugo to the alchemist who made the potion he used on Thierry in order to use it on Peewit's alleged rival, if they agree not to go to Genoveva.
At night, Johan returns to the inn to warn Thierry that they will be gone for a few days to seek the potion, then pays the innkeeper to watch the dog for a few more days, unaware his stunned host has overheard him talking with Thierry. Johan, Peewit and Hugo leave the following day, while Maltrochu goes to repeat his marriage proposal to Genoveva. Meanwhile, the innkeeper talks about the talking dog to his disbelieving friend Julio, who nonetheless spreads the rumor throughout the town.
Three days later, Johan and company arrive at the alchemist's house and receive the potion. Two more days later, Maltrochu returns to his castle and hears the rumors from town about the innkeeper who believes a dog he has been entrusted with talks. When Johan and Peewit come back to the inn, they discover that Maltrochu has caught Thierry and ordered for them to be arrested and hanged, but they manage to escape.
The only way to solve everything is to get the antidote, so Johan and Peewit go to Homnibus' house. Homnibus analyzes the formula to make an antidote, but he needs a volunteer to test it. Peewit tries to use Oliver as a guinea pig, but Johan decides it's more democratic to decide by the shortest straw. Peewit loses and drinks the potion to become a dog, but then the antidote doesn't work. After other failed attempts, Homnibus decides to send a stork with a message to Papa Smurf.
Meawhile, Maltrochu tries to convince Genoveva that the dog he has brought is her beloved Thierry under a spell, but the knight cum pooch just barks until his rival force-feeds him wine to get him drunk. When Thierry talks, proving Maltrochu's claims to Genoveva, the evil Baron promises her he will have her beloved turned back to normal if she marries him. Later Oliver, while shopping at the market on Villers, overhears people talking about the sudden announcement of Maltrochu and Genoveva getting married three days from now, and returns to Homnibus' house with the news. Right then, Papa Smurf arrives along with a group of Smurfs. Papa Smurf and Homnibus work together to make the antidote, which works this time. The Smurfs go ahead riding storks to Maltrochu's castle to check what's happening, while Johan and Peewit stop at an inn, where they meet Bertrand, a friend of Thierry, to whom they tell what has happened and he decides to accompany them to the castle at dawn.
The following day, Bertrand arrives with a group of friends to help Johan and Peewit. The Smurfs inform them that Maltrochu left with a dozen men but Thierry is still locked up at the castle. When Bertrand and his friends try to understand the Smurf language, Peewit explains them that, por ejemplo, "I smurf to the smurf" es "I go to the woods", but a Smurf corrects him that "I go to the woods" is told "I smurf to the smurf" while "I smurf to the smurf" means "I warble at aurora", which confuses all the humans present since it all sounds the same to them.
The storks carry the Smurfs to the castle chimney and they throw down a rope to allowing Johan and the others to climb in, and then face the remaining guards of Maltrochu. After they and their comrades win the fight, Johan and Peewit go to the dungeon and give Thierry the antidote, restoring him at last. They ride all night and arrive at Genoveva's father's castle the following day, just in time to stop the wedding. Thierry uses Johan's sword to face Maltrochu, who after finding himself defeated, decides to confess. The wedding goes ahead, but with a different groom.
Johan and Peewit return home, while the Smurfs have already gone back to their country. Thierry finds Genoveva a very demanding wife, so he just answers her by barking (though the epilogue states they were very happy and had a lot of children).
- Even though the Smurf still are mere secondary characters, they have a somewhat larger role in this story than their cameo appearance in The War of the Seven Springs.
- This story was reprinted in English by Papercutz in The Smurfs Anthology Volume 4.
- This was the last Johan and Peewit long story which was created by Peyo and published by Dupuis as Peyo did not continue this series. The next comic story, The Raven's Horde, was created after Peyo's death and published by another company called Le Lombard.