Spoilers for this episode.
Jack and Kate survive the Russian ambush with CIA backup, but Cheng has discovered the tracker in the override device and leaves Open Cell with Chloe. Jack reaches the abandoned base and finds a recording she made, allowing him to identify Cheng's voice. The attack on the Chinese carrier brings both countries toward war. Heller needs evidence of Cheng's involvement to persuade China that the submarine's order was forged rather than a deliberate American strike.
Jack traces the Russians' access to his movements back to Mark. Confronted in front of Heller, Mark admits forging the order to surrender Jack and cooperating with Anatol Stolnavich. Jack recognises Stolnavich as an intelligence operative with a connection to Cheng and uses Mark to approach him. Wearing a camera and earpiece, Mark claims he wants to defect. His visit gives Jack and Kate a view of the house's security so they can enter and search for Cheng's location.
Stolnavich discovers the deception and fights Mark while Jack and Kate close in. Broken glass pierces his neck, and he dies before Jack can question him. Chloe escapes Cheng's moving vehicle and tumbles down a wooded slope; his men fail to find her. Audrey arranges a meeting with a Chinese contact to help establish Cheng's responsibility, but gunfire kills the contact and her security team. Cheng calls Audrey and warns her to cooperate or be killed. Jack still needs to locate Cheng, while Audrey is trapped.