Sheppard, Teyla, McKay and Ronon arrive at a village led by a jovial baker named Lucius Luvin, who shows off his six wives while urging the team to trade their ship for a few local herbs. Unimpressed with his preposterous offer, the team soon departs. In case Lucius's herbs are actually of medicinal value, however, Dr. Beckett visits the village to investigate.
After a long delay, Beckett returns to Atlantis - with Lucius. Because the Ancient city's safety depends on its secret existence, Weir is appalled at the doctor's thoughtless breach of security, but Beckett insists that Lucius is worth it. Despite her concern that Beckett is acting less like his usual rational self and more like a fawning schoolboy, Weir agrees to meet with the baker. But later, when Sheppard and McKay return from another mission, they find Weir, Teyla, Ronon and the rest of Atlantis's personnel obeying Lucius's every command with besotted obedience. Although they can't guess how or why he's doing it, Sheppard and McKay realize that, clearly, Lucius is controlling people's minds.
McKay spots the baker drinking a mysterious potion and steals a small sample for analysis. He needs more of the substance to complete his research, however, so Sheppard returns to the village. There, he finds Lucius's doting wives and friends pining for his return, even growing physically ill - as if they're in withdrawal from drug addiction. They eagerly give him a sample of Lucius's "daily medicine" after Sheppard promises to bring their beloved baker home.
Back at Atlantis, Sheppard finds that McKay, too, has become one of Lucius's mindless minions. Worse, Lucius has sent Beckett, Teyla and Ronon on an irresponsible mission to a Wraith-dominated planet. By sheer luck, they return unharmed after a fierce battle, jubilant to give their beloved Lucius a rare herb he asked them to collect there.
Reluctantly, Sheppard plays along with his friends' insanity until he can steal McKay's half-finished research, abduct Beckett, and fly him to the mainland. There, as Beckett struggles through withdrawal, Sheppard pieces together Lucius's secret. The potion - made with the herbs from the Wraith planet - allows Lucius to secrete a pheromone that stimulates the prefrontal cortex in the brains of people nearby, resulting in euphoric emotions and extreme suggestibility. Sheppard hasn't inhaled much of the chemical so far, but that's about to change: Teyla, Ronon and McKay are hunting for him. When they capture him, it won't be long before he, too, succumbs to Lucius's overwhelming charm.