Sheppard's team is traveling to a village after the MALP detects life signs. They find a prospering township and a cheery baker, Lucius Lavin, who introduces himself and his six wives as the villagers cheerfully acknowledge his authority. Lucius flirts with Teyla but is surprised that the Atlantis team hasn't heard of him. When they leave to check out the village, he takes a swig of liquid from a bottle.
Lucius treats them to a meal while he considers Teyla's potential as a new wife. He notices that Sheppard has a cold and offers him some medicinal herbs in return for their Puddle Jumper. The team is put off by his eagerness and leave but promise to send a team back, much to Lucius' relief.
Sheppard reports to Weir and reluctantly suggests they send someone back to check out the herbs. Dr. Beckett goes to check them out and Lucius offers him his healing potions in return for the contents of Beckett's backpack. Beckett declines while back at Atlantis, Rodney is working on the project to set up a "bridge" of Stargates from Earth to Atlantis. At the village, Lucius is regaling the village with one of his miraculous healings as Beckett looks on, enraptured. Lucius is still interested in the Puddle Jumpers and takes Lucius back with him through the gate to Atlantis.
After putting Lucius in confinement, Weir demands answers from Lucius and wonders why Beckett brought him to Atlantis despite the security protocols. Beckett is enthused about what Lucius can do for them but everyone wonders why he's acting so smitten. Sheppard and McKay go on another mission while Beckett shows Lucius to his new quarters. When Lucius tries to go on a tour, Ronon and Teyla intercept him but he convinces them to give him a tour. Beckett convinces Weir to interview Lucius and he goes to meet with her after taking another sip of liquid.
Weir tries to get Lucius to talk about his proposed alliance but it doesn't seem like much. Later McKay and Rodney arrive to find to find everyone gathered in the mess hall listening to Lucius telling a story as everyone else looks on in fascination, including Weir, Ronon, and Teyla.
When Sheppard and McKay try to get answers, Weir and the others are unbelievably enthused and Teyla is now eager to become his wife. Rodney checks the surveillance footage and finds the liquid that Lucius is drinking. Rodney starts to break it down while Lucius has Weir and Zelenka show them the gate-bridge program. Lucius proposes a planet to them that he says is empty but Sheppard has reports that the Wraith have occupied it. Sheppard overrides Weir's authority and after he leaves, Lucius suggests she "do" something about him if he doesn't come around.
Rodney continues to try and break down Lucius' liquid and Sheppard has to go back to get more of the liquid for samples. When he returns he finds the villagers depressed and clearly undergoing withdrawal. They all call for him to bring Lucius back to them and his wife Willa mentions an accidental discovery he made and after that the villagers all loved him. They get the liquid in return for his promise to bring Lucius back.
When Sheppard returns, he finds that McKay has fallen under Lucius' sway. Rodney reveals that Ronon, Teyla, and Beckett went to the planet to get a rare herb for Lucius. A few minutes later they come charging through the gate, laughing good-heartedly as they get through ahead of Wraith energy blasts. When Sheppard tries to grab the herbs Ronon draws his gun and Lucius starts to turn the others against him. Sheppard plays along and goes voluntarily to his quarters. Beckett tells Lucius about the gene treatment and he and McKay show Lucius the Puddle Jumper.
Later Sheppard talks to Beckett and admits there's something wrong with him. Once he gets Beckett alone, he stuns him and takes him to the mainland in a Puddle Jumper. They quickly figure out Sheppard took the ship and McKay's computer with his partially finished research.
On the mainland, Sheppard tries to complete McKay's research while Beckett goes through withdrawal. He concludes the liquid causes the excretion of a pheromone that stimulates positive emotions in others, and it's extracted from the herb he sent the others to collect. Since Sheppard had the cold and hasn't been around much, he's been unaffected so far. Ronon, McKay, and Teyla search for Sheppard and get the drop on him.
Lucius confronts Sheppard in his cell and reveals that the Wraith set up an outpost on the planet where he found the herb, and he had a new resource to get more of it. He plans to expose Sheppard to more of the pheromone once he gets over his cold. Lucius then goes to get the gene injection from Beckett. It takes and he prepares to leave in a Puddle Jumper, but Sheppard grabs him--Beckett reveals he gave Lucius a neutralizer for the pheromone instead of the gene treatment. Sheppard takes off in the Puddle Jumper with Lucius while Beckett gives the rest of the Atlantis crew the cure. Sheppard prepares to take Lucius back to the village…after they give the serum to the villagers.
Sheppard's team returns later to report that the villagers have recovered and plan to punish Lucius. Everyone's back to normal although Sheppard starts doing favors for McKay and it becomes clear Rodney has kept a little bit for himself, which Weir tells him to burn.