At the point where Dr. Charlatan enters the story, he has been driven out of a human community for selling his "miracle tonic" and was in the Smurf forest trying to figure out what to do when he comes across Sickly Smurf wandering in the forest. Reading from his books that Smurfs are known to be able to cure every known disease, Dr. Charlatan decides to become friends with Sickly and offers him a whiff of his "miracle tonic" to cure what he diagnosed as "smurfaworphalitis". After experiencing his symptoms going away, Sickly brings Dr. Charlatan into the village to introduce him to the rest of the Smurfs, where he offers them samples of his "miracle tonic". Soon the rest of the village takes him up on the offer except for Smurfette, who suspects that something about Dr. Charlatan just isn't right.
Throughout the time Dr. Charlatan has interacted with the Smurfs, Smurfette has seen that her fellow Smurfs are being duped by the promises of the "miracle tonic", seeing no real improvement of what they claimed was improved -- Farmer's crops, Greedy's food, and Brainy's intelligence level -- while the imp was bleeding them dry of their possessions. Smurfette tries to reason with Sickly, who ends up going off to Gargamel's to dare Azrael to chase him. However, as Azrael gives chase to Sickly, he finds out that his sickness was never really cured by the "miracle tonic" and is soon captured by Gargamel. Meanwhile, the Smurfs appear unto Dr. Charlatan and tell him they have nothing more to give to him for the "miracle tonic". Deciding it was now time to capture them for his purposes, he deceives the Smurfs into entering a giant cauldron for a free fillup of "miracle tonic".
Smurfette has told what had happened to Papa Smurf, who has returned from his visit to Malchior who also was Dr. Charlatan's customer, and as the both of them see Dr. Charlatan capturing all the Smurfs in his cauldron to use them for a real miracle cure, Papa Smurf has Smurfette distract Gargamel while he deals with the imp. He tells Dr. Charlatan that he may have contracted a possibly fatal disease from contact with the Smurfs called "smurfonia" and offers to give him a cure for a thousand gold pieces. When Dr. Charlatan says he could only offer Papa Smurf a few coppers, the village leader decides on an alternate form of payment. This required Dr. Charlatan going to Gargamel to convince the wizard that his recent pains and aches are the result of a disease called "sorceritis" and offering his "miracle tonic" in exchange for the two Smurfs, Sickly and Smurfette, whom he had captured.
With Sickly and Smurfette returned to Papa Smurf, the village leader gives Dr. Charlatan the cure for his "smurfonia" which he pours on his head. However, with the next words that came out of the imp's mouth, he realizes that he himself has been duped -- Papa Smurf has given him a "miracle cure" for his lying, which means that he would go broke, unless he decides to become a real doctor.