At a tavern, Vala meets with a smuggler, Ta'seem, and wagers a cloaking device against his cargo ship in a game of skill and luck. Vala wins but Ta'seem has her searched and figures out she was cheating. They're interrupted when Adria arrives and telekinetically shoves Ta'seem and his men away. She warns Vala that their attempts to destroy the Ori failed and they plan to invade and conquer. Adria demands to know why Vala is alone, forcing her to explain that she went to Daniel to tell him that she knows where the Clava Thessara Infinitas is, having gotten the information in a dream. SG-1 wonders if Adria planted the dream but conclude that it is a memory that Athena dredged up from her mind probe/interrogation. Landry sends SG-3 and 8, but they return under enemy fire and Colonel Reynolds the Ori were waiting for them. The next night, Vala gives them a new dream with different Gate coordinates, but they figure it's a set-up by Vala to pick them off and everyone leaves Vala alone. Vala then relates how the IOA labeled her as a security risk and had her removed from the team and imprisoned.
Adria uses telepathy to determine that Vala is telling the truth. Vala then tells of how she used the cloaking device to escape through the Stargate when another team left. Adria wants Vala to join with her and seek out the Infinitas. Vala reveals that SG-1 plans to check out the second set of coordinates, and Adria forces Vala to admit they are taking a ship so they'll beat them if they go by Stargate.
Vala and Adria arrive through the Stargate only to find SG teams waiting for them with an anti-Prior device to inhibit her powers. Jaffa arrive and announce that Ba'al, their master, has the area targeted from orbit and will destroy them all. They then take Adria with them as they teleport out. Ba'al greets Adria and notes that he won't have to restrain her powers for long.
Back at SGC, Mitchell informs Landry of what happened and they wonder what Ba'al has planned. Sam and Daniel explain to a furious Vala that her false memories are all part of the plan. Before changing her memories, Vala made a recording to explain to her present-self that she came up with the plan to alter the memories. They planted Vala on Adria to lure her into a trap.
Ba'al tells the captured Adria that her armies will never find her and if they look for her, they'll suspect the Tauri. Ba'al announces that he plans to use her to take control of his army and flashes his symbiote eyes at her.
Landry is meeting with Flemming who has an undercover agent in Ba'al's Earth operation. The Ba'al clones plan to meet on a planet and SG-1 goes there only to find all of the Jaffa dead, of symbiote poisoning. They also find all of the Ba'al clones dead of the same poison. Aboard Ba'al's ship, a Jaffa brings in a symbiote and prepares to insert it into Adria.
SG-1 finds one living Jaffa who reveals that Ba'al was responsible for the attack and the Jaffa survived because he uses the anti-symbiote medication, and gives them the coordinates to Ba'al's location. SG-1 leaves in the Odyssey and plans to beam aboard Ba'al's ship and scan for the anti-Ori energies to find her location. After the meeting, Mitchell suggests that Vala sit out the meeting as they may have to kill Adria, but Vala is seemingly okay with that. Cloaked, they approach Ba'al's ship and pinpoint Adria's location. They burst in, shoot down Ba'al and the guards, and zat-stun Adria, then beam out with her.
Later on the Odyssey, they wake up Adria whose eyes glow: the Ba'al symbiote is now in her. The team brief Landry and suggest that they suppress Ba'al's symbiote and have a Tokra symbiote take her over. Ba'al-as-Adria suggests they let him go through with his plan to order the Ori out of the galaxy, but they note they plan to have the Tok'ra do it. Ba'al threatens to kill Adria as soon as they try to remove him, costing them all of the knowledge Adria possesses.
The Tokra contingent arrives led by Ta'seem who will conduct the surgery. He warns that the extraction procedure is difficult and Adria may not survive. They zat-stun Adria and begin the operation. Vala refuses to watch the operation and Daniel goes to comfort her. Daniel wonders if she truly doesn't feel anything about Adria's fate but Vala is insistent.
Adria's body starts to shut down and it turns out that Ba'al released the toxin into Adria's body, killing her. Her body is too weak to support a Tokra symbiote and Ta'seem recommends that they administer a stronger dost of the toxin, killing her. Vala agrees and says goodbye over the unconscious Adria, then sits and watches as Ta'seem gives the injection. Adria wakes up just as he does so, knocks Ta'seem and the guards away, and breaks free. She seals the sickbay doors, trapping Daniel nearby, and jams the teleportation system. The weakened Adria admits her body is dying and she wants to use her remaining time to prepare for Ascension, with Vala as her witness.
As Mitchell tries to burn through the doors to get to Daniel, Daniel figures out what Adria is trying to do while Vala tries to appeal to Adria's compassion as part of her human side. Mitchell cuts through the first door but the internal door is sealed and Adria is holding it shut with her mind so they can't use the override codes. Adria knows what SG-1 is doing and causes a coolant link to distract them with toxic gas. While Sam reroutes the fluid, Mitchell and Teal'c try to get through. Daniel calls out to Vala, who tries to get Adria to stop by shooting her. Adria holds Vala at bay while Sam reroutes the coolant fluid, saving Daniel. Adria prepares to kill Vala but then collapses. Vala looks on as Adria glows with a bright light then disappears.
Back at SGC, the team considers the repercussion of Adria's ascension, and they conclude she's either leading the Ori forces, or taking on all the power of the defeated Ori. Worse, they figure they may not have killed the real Ba'al. Still, Vala assures them that they've dealt both their opponents a serious blow.