The book takes place in London, United Kingdom, after a worldwide sickness has infected adults, turning them into something akin to voracious, cannibalistic zombies.

During the ensuing fight, Deke is killed when his lung is punctured by a shard of glass, and Arran is bitten by a zombie he believes to be his mother.

Later that night, they save a boy named Jester from a large pack of zombies, prompting him to invite the group to his home, Buckingham Palace, which he claims is safe.

Meanwhile, Small Sam, a young boy who was kidnapped earlier by adults (leading the rest of the Waitrose group to believe he is dead), awakens in a zombie nesting ground at Emirates Stadium.

He is saved by an apparently uninfected man named Nick, who takes him to the carriage which he and his also-uninfected wife Rachel are using as a home.

The Holloway children eventually force the zombie army into a retreat, but Arran's bite causes him to go insane and chase after them.

He is mistaken for a zombie by a girl named Sophie (leader of a group of archers) and she shoots him in the chest with a bow and arrow.

They also encounter a small group of kids being attacked by extremely strong zombies, and fail to save all but one of them, an unnamed girl who is bandaged and taken along with them.

The bandaged girl is put in the infirmary, whilst the rest of the group are given a tour of the palace, where they are shown the infected royal family (who are kept in the throne room, too weak to fight back).

Back at the palace, David declares that due to the casualties, the ownership of the park will be decided in a fight to the death between Achilleus and John.

They free the royals, causing chaos, and fight their way through David's forces, eventually making it out (with Paddy and a guard known as Big Nose coming along with them).

They are met by a group of people led by a boy with a scarred face, later known as Ed, who take them back to their home in the Tower of London.

Eventually, the same army from before (led by Saint George) storm the Waitrose supermarket, and Callum lets them kill him to end his suffering.

Disney Hyperion, the series' American publisher, wanted to target the books at a slightly older audience.

Additionally, some of the cultural references and terminology unique to the United Kingdom were changed to ones that American readers were more likely to understand.