As British Prime Minister Robert Sutherland returns from his daughter Ellie’s graduation from the University of Liverpool, his chief of staff Anna Marshall calls him to say an impending threat has been upgraded to significant. Convene a full COBRA—Cabinet Office Briefing Room A—in the morning, he says, as he boards a helicopter.
The threat is a solar storm that could knock out satellites in its first phase, throwing the world’s navigation systems out of order. Even more serious is the second phase, in which a plasma eruption could pitch areas of the globe into a complete blackout—for months. It all depends on whether the eruption heads towards Earth, and its magnetic orientation. There’s a 50/50 chance it will disrupt power grids—but there will only be a half-hour’s notice.
Unfortunately for the PM, he doesn’t have the full support of his government. The Home Secretary, Archie Glover-Morgan, is a hardline Conservative who doubts the solar storm will end up causing significant chaos, while Robert and Anna are reformist Tories. Plus, they have just angered Archie by firing a policy aide aligned with him, Dominic Knight. Anna shocks Archie by suggesting she’ll replace Dominic with Francine Bridge, a Labour MP who recently resigned.
Robert thinks Anna is joking in her suggestion of Francine, but she’s not. She sets out to convince Francine to take the job, but Francine is completely opposed. After a long back-and-forth on the merits, Anna changes the subject and mentions her time as a war reporter in Bosnia in the 1990s. She knew a local translator who disappeared after he went looking for his sister, and hadn’t seen him since—until he showed up on her doorstep the other day. He wrote letters, but Anna ignored them, and she asks him to leave her alone.
But there are more urgent matters for Anna to worry about. The solar threat has been upgraded to serious: a plasma eruption is headed towards Earth. While it remains to be seen if it will extensively knock out power systems, the solar storm is already affecting airplanes. France has been especially disrupted, and is sending flights to land in the UK, but the Prime Minister decides not to ground flights yet because of the chaos it would cause.
As the day progresses, French planes begin getting lost as their navigation systems go down. One flight, low on fuel, desperately asks for a closer landing strip as their electronics fail over Northumberland. Running out of time, the pilots try to crash land in a field, following the lights of a highway. But they descend too quickly and smash into the road, just ahead of Stuart Collier, the chief constable of the area.
Stuart walks through the wreckage, calling in help. Hearing a woman cry out for her baby, he searches through an intact part of the plane to find the sobbing infant, who is amazingly unharmed. Emergency vehicles appear at the horrific scene. Twenty-five people have died; that number is expected to rise.
Meanwhile, members of COBRA prepare for a potential crisis. Fraser Walker, who is leading briefings about the solar threat, briefly leaves to walk his father’s dog; his father recently moved into a care facility. He also calls his estranged ex-wife, warning her to prepare for the worst and keep the kids safe.
Archie meets with Dominic Knight, and they gossip about rumors that Anna and Robert were in a relationship when they were younger. Dom asks Archie, “When will you make your move?”
Archie also warns Anna not to appoint Francine; she retaliates by noting rumors of him being handsy with women, infuriating him.
Anna has received a note on her doorstep along with a Bosnian delicacy: I’m leaving tomorrow, it says. Please come see me. As her children sample the Bosnian food, Anna learns that her husband’s plane has been diverted to land in Portugal. And then she gets a call about the French plane crash, and rushes to COBRA.
As Robert prepares to address the crash, his wife gets a call from his daughter Ellie. She and her friends were taking drugs, and now one of them has gone into a coma. Ellie is at the hospital, distraught. Robert has to deal with the solar threat, so his wife will go to Liverpool to calm Ellie; Robert will send his press secretary, Peter Mott, to help in the morning.
COBRA convenes and they wait for the plasma eruption to get close enough to determine what effect it will have. As it passes their satellites, they get a prognosis: huge blackouts are coming, in only half an hour. France and Spain are already losing power, and the entire system is on the brink of collapse—worse even than predicted. Robert declares a national emergency.
Francine calls Anna from her balcony. She’s given the job offer more thought, she says in a voicemail. And then the lights of London flicker off. The city has lost all power.