|Series 9, Episode 4|
|Series 09, Episode 04|
|Air Date||11 October 2010|
|Previous||Series 9, Episode 3|
|Next||Series 9, Episode 5|
A trio of highly skilled Chinese agents arrive in the UK to kidnap and assassinate Dr. Jiang (Daphne Cheung), a scientist developing revolutionary desalination technology. Beth turns Kai (Benedict Wong), a diplomat in the Chinese embassy, into an asset. Lucas and Dimitri break into the Chinese embassy to steal information regarding the agents.
Ruth goes undercover in the company's building to access their computers for Tariq. Kai informs MI-5 of a bomb in the same building; Jiang is working there. MI-5 jams radio frequencies around the building to prevent remote detonation. Ruth learning of the bomb, locates Jiang with the intention of getting her out of the building but she is in the custody of CIA agents. The agents are informed of a very secret safe house that CIA London HQ will reveal as they drive there with Jiang, Ruth, and Lucas.
The CIA agents were set up; the Chinese, knowing that MI-5 would block the airwaves to prevent remote detonation, tricked the CIA with a fake broadcast, and kidnap Jiang. In response, MI-5 lets the Chinese intercept false intel through Kai indicating that the Home Secretary will authorise a breach of the embassy to rescue Jiang. The Chinese take the bait, and move Jiang, and Kai, who is under arrest, to the airport. The Section D team intercepts the Chinese van, and seizes Jiang and Kai. The head of Chinese intelligence in London informs Harry that if they do not hand in Jiang back to the Chinese, they will detonate a bomb in London.
Dimitri finds the bomb and disarms it with Tariq's help. Jiang is transferred to the CIA. Kai, who can have freedom in London, misses his homeland, and voluntarily turns himself in to the Chinese embassy. Lucas obtains the Albany file by logging in to the network using the ID and password of Stephen Owen, another MI-5 agent. He also transfers a considerable amount of money into Owen's bank account, apparently setting the agent up for a fall. Lucas delivers the Albany file to Vaughn. Believing he is free from Vaughn, and allowing him to restart his relationship with Maya. Although reported to have left the UK, the Chinese agents reveal that their mission is in fact to track and kill Lucas for undisclosed reasons.