 SG-1 learns that the whereabouts of Merlin s weapon (which should be able to defeat the Ori) is most likely on Atlantis, Daniel and Vala visit Earth s base team there. Meanwhile, its scientific top brain Dr. Rodney McKay is detailed back on the Odyssey with Lt. Colonels Sam Carter and Cam Mitchell, who are trying to reroute the super-Stargate through which they fear the Ori are about to send reinforcement ships, despite the danger of using nuclear explosions so close to a black hole. Daniel gets answers from the database, but figures out they don t come through a hologram but from an ascended Ancient: Morgan le Fay!