While the mysterious kidnapper breaks into Michael's home to steal a photo of Laurie Dupree, Michael and Maria break into the Dupree home to find Laurie both scared and unstable. When they are caught by Laurie's Aunt and Uncle, they are escorted off the premises. Meanwhile Sheriff Valenti and Agent Duff pull over Grant Sorenson and serve him a warrant to search his car. When Grant is unable to explain a pair of gloves and a few scratches on his neck, he defends himself by telling Duff Valenti has been persecuting him since day one. Maria and Michael decide to go to the local records office, and discover that Laurie is the rightful owner to the Dupree estate. They go back to the Dupree estate with what they've discovered, and are invited to stay as guests. Maria reveals to Meredith Dupree she knows the Duprees paid off doctors to say Laurie was insane so they could have all the money to themselves. In a bomb shelter under the Dupree estate, Michael and Laurie discuss Grandpa Dupree. Laurie shows Michael old notebooks her Grandfather used to keep, explaining how he claimed to be abducted and how it eventually drove him insane. Michael realizes that Laurie and her Grandfather contain the genetic defect the Gandarium need to survive. Michael then tells Laurie she's not crazy, and what happened to her was real. He also tells her she has a right to take back what is hers, including the house and her life.
At the Crashdown, Max, Liz, Tess and Isabel meet to discuss what Larek told them about the Gandarium. Brody shows up as Larek and explains how the Gandarium are a genetically engineered life form used to bridge together alien and human DNA in order to make alien hybrids. He goes on to say they will infect only certain humans who have a defect they can grab on to, in this case, Laurie Dupree, and the infected human will eventually die. Tess and Liz realize the Gandarium have not finished what they started on Laurie; that's why they are still after her. Larek then explains there is a queen and a hive, and if they can find and destroy the queen the rest of the Gandarium will die. Max tells everyone to meet in Frazier Woods to look for the crystals' nest. At Frazier Woods when Kyle and Alex help to look for the crystals, they discover a cave, the nest, and eventually become trapped inside. Kyle calls Liz to tell her where they are, and explains they are unable to get out. Max, Isabel and Tess attempt to use their powers to break into the cave, but their powers have no effect. Isabel leaves to get equipment to help rescue Kyle and Alex while Max, Liz and Tess try to dig them out. Inside the cave, Alex and Kyle discover the Gandarium die without oxygen.
Back at the UFO Center, Isabel is drugged and kidnapped by Grant. She later awakens to find him rambling that he doesn't remember everything that's been going on with him, and he begs her to help him. Isabel realizes Grant was infected by the Gandarium when he was digging at Puhlman Ranch over the summer, and concludes the queen must be inside of him. Grant then tells Isabel he is supposed to kill her, but can't bring himself to do it. He lets her out of the car, and she calls Valenti telling him to get to the Dupree estate to stop Grant from killing Laurie. Valenti goes to Agent Duff and explains the situation, asking her to come to Tucson with him. At the Dupree estate while lounging at the pool, Michael gets a call from Max who tells him what they learned about the Gandarium needing oxygen to survive. Feeling they are safe, Maria, Laurie and Michael then enjoy an extravagant dinner. Upon orders from Maria, Michael goes to find the maid and discovers she's been killed. He then tells Maria to take Laurie to a safe place and goes looking for the intruder. While Maria and Laurie flee to the bomb shelter, Michael is shot by Grant.
Grant reaches Laurie, just as Valenti and Duff show up at the estate and find Michael shot on the floor. Michael tells them to go after Grant who is holding Laurie hostage. Duff shoots Grant and everyone watches as the queen of the Gandarium comes out from his body. Remembering what Max told him, Michael closes the queen in and uses his powers to suck the oxygen from the room. The queen then dies, thus killing the hive and freeing Alex and Kyle. Not knowing what she's seen, Valenti tells Duff sometimes things are better left untold, especially if she wants to keep her career intact. Michael tells a now safe Laurie Dupree goodbye.