Sydney's emotions are turned inside-out when she comes face-to-face with Allison, Francie's doppelgänger, who was presumed dead but is now a key figure in The Covenant. Meanwhile Lauren's search for Lazarey's murderer leads her closer to discovering a connection to Sydney, and Sydney begrudgingly is assigned as Sloane's CIA handler.

The identity of the mysterious "St. Aidan" forces Sydney to pull a stunned Will out of witness protection. But the pursuit sends the two old friends on a collision course with Allison -- the woman who ruined both their lives. Meanwhile, a zealous Lindsey arrests Jack and Vaughn as conspirators in Sydney's escape from NSC custody, Sloane, still under pressure from Lindsey, puts a plan in motion to eliminate Sydney, and Dr. Brezzel has an unpleasant run-in with Sark.