There’s been a slight earthquake off the coast of Kent, which wouldn’t normally be a cause for concern—but there’s an old World War II ship carrying munitions wrecked on the seafloor, and the quake might have damaged the hull of the ship. More tremors might come and cause the ship to explode, but it’s uncertain how likely such an outcome is, as Fraser Walker, the man tasked to monitor such emergencies, explains to the Prime Minister Robert Sutherland and his COBRA (Cabinet Office Briefing Room A). The COBRA is led by Robert’s new Home Secretary, Joseph Obasi, who is popular with the Tory party base—he cites St. Paul to Robert—although Robert’s right-hand woman, Anna Marshall, is uncertain about him.
The government decides to institute a mandatory evacuation, given that an explosion could “reshape” the coastline, in Fraser’s words. A mandate is the only way they will be able to get some resisters and elderly people to leave for safety.
A less obvious crisis has also sparked. The helicopter of an oligarch named Kostenko has been shot down by a drone as it took off from the field of a school next to Twickenham stadium, killing Kostenko and his companions as well as a rugby coach at the school.
That innocent death of the volunteer coach makes Robert eager to act in the wake of the incident, despite the geopolitical implications—and there are many. Kostenko has hosted numerous powerful politicians on his yacht, including Archie Glover-Morgan, Robert’s former Home Secretary and political rival. Kostenko also managed to make enemies in both the Ukrainian and Russian governments, and is tied up in corruption cases involving the leaders of Israel and Brazil. Then there’s the bad-looking business of oligarchs getting to use a school’s field to launch their helicopters during rugby games.
Eleanor James, Robert’s intelligence director, has learned that a Russian woman named Klara Lechkova was probably responsible for the drone hit: she is seen on CCTV around the school and had just bought a scooter to use in her escape. Her uncle is a member of the Russian Duma, with ties to separatists in the contested Donetsk region of Ukraine. Her accomplice, the Moscow-educated Rodrigo Araya, is the son of a killed Colombian paramilitary. The pair hasn’t left England yet.
Eleanor thinks it would be easiest to let them go, given their connections to the Russian government, but Robert decides to have them arrested. A plan is devised to test the geopolitical response: Lechkkova is framed and then arrested for shoplifting at the airport, while Araya, who fled when Lechkova was confronted, is taken in for resisting arrest. He calls out to onlookers that he’s a Colombian human rights activist as armed police bear down on him.
Robert also faces a possible test in political support. He only narrowly won a majority in Parliament, and Archie still retains a seat—even if he only won by seventeen votes. Archie of course is maneuvering for more influence and wants a seat in the Cabinet. He meets with Robert’s onetime press secretary Peter Mott, who has been cleared of wrongdoing associated with his involvement in a scandal involving Robert’s daughter Ellie but remains “unemployable,” as Archie points out.
Robert’s wife Rachel is also not sure she will be able to work as a lawyer again in the wake of the Ellie scandal, although the trial against her collapsed. Instead, she’s eager to plan a holiday visit with Robert to Ellie, who is abroad and has a new radical activist boyfriend.
The Labour Party defector Francine Bridge is asked her opinion on all these trials and inquiries by a radio interviewer, given that she resigned from Robert’s government over the shooting of a photographer by the military as they broke a blockade in order to restore power to the north of England. She has a drink with the journalist after the interview, but despite his interest in her, she leaves him for an early night. As she departs, he receives a tip announcing Lechkova and Araya as Kostenko’s killers.
Things didn’t work out between Fraser and Francine romantically, as Fraser tells his aide Audrey Hemmings while they begin instituting the evacuation in Kent. Audrey shares her own personal life, talking fondly of her father, who died alone in the hospital.
Fraser trusts Audrey, but Mark Everly, the naval commander in charge of investigating the WWII wreck, dismisses her, both because she’s a young woman and because he doesn’t like civilian interference in his work. Nonetheless, she holds her own as she joins him on a boat while divers examine the wreck.
While the divers are at the wreck, the navy picks up strange readings—and suddenly the wreck explodes, sending a spray of water and debris over everything and a shock wave that knocks Fraser against his car back on shore. He yells at people who refused to evacuate and were walking on the beach to run to higher ground and then speeds off in his car.
He tries to outrun a huge wave generated by the explosion but is hit by it while driving through a tunnel. As his car fills up with water, he smashes the window and climbs on top of his car.
Audrey is alive, but has a nasty head wound and is flailing to stay afloat amongst debris in the water. She slowly loses energy and begins to sink.
Robert and his team back in London can’t track any of this, although they know there have already been mass casualties. A massive cyber attack unlike any Eleanor’s team has ever seen has taken down communications with the emergency response team. Anna suggests that it’s retaliation for the arrests of Lechkova and Araya. Embedded in the code is a message: “Ruin Britannia.”