Spoilers for this episode.
Collette's accusation puts Audrey in a CTU holding room while investigators search for links to Henderson and Cummings. Jack questions her himself and learns she had an affair with Cummings, but he concludes that she knows nothing about the terrorist plot. Karen Hayes remains unconvinced and orders Burke to resume the interrogation with drugs. When Jack tries to remove Audrey, Burke shocks him with a taser and the guards restrain him instead.
Chloe finds calls between Henderson and Collette, giving Jack grounds to challenge the broker's immunity agreement. Jack confronts Collette at gunpoint, and she admits Henderson told her to name Audrey. She finally identifies a natural gas distribution center as Bierko's target. Elsewhere, Aaron searches for the missing Wayne and finds him in the woods. They escape the gunmen hunting Wayne, while Henderson continues directing the effort to kill him.
Bierko's men murder police officers and use their uniforms and vehicle to reach the Wilshire Gas Company. They force an employee to prepare the system for Sentox, planning to send the nerve agent through household gas pipes. Jack reaches the facility too late to stop it entering the system. He rigs an explosion to burn the contaminated gas before it leaves, then pursues Bierko as the plant erupts. The hour ends with both men caught amid falling debris.