The SG-1 team travels to Atlantis to attempt to establish a stable wormhole to the Ori supergate, which will prevent the Ori from sending more ships to Earth's galaxy. In order to do so, Carter (Amanda Tapping) and McKay (David Hewlett) must detonate precisely calibrated nuclear warheads to cause a wormhole to jump from a nearby spacegate to the supergate, without destroying their ship, the Odyssey, in the process.Meanwhile, Daniel (Michael Shanks) and Vala (Claudia Black) take advantage of their time at Atlantis to research the Atlantis database for clues to the location of Merlin's weapon. During their research, they are met by Morgan Le Fay, an ascended Ancient posing as the Lantian holographic interface, who gives them the names of two planets where the device might be located. But can she be trusted? Weir (Tori Higginson) detects a Wraith ship headed towards the Odyssey, and is unable to relay the message due to the interference of the nearby black hole. And the Odyssey detects an Ori ship headed toward the supergate. Will the team be able to complete their mission before they are attacked?