Set a year after the events of the first book, it follows three Bayview High students—Maeve Rojas, Knox Myers, and Phoebe Lawton—as an anonymous texter begins a game of truth or dare that has fatal consequences.

The novel formed the basis for the eight-episode second season of the teen drama mystery television series One of Us Is Lying, which was released to the streaming service Peacock on October 7, 2021.

Maeve Rojas—sister of Bronwyn Rojas, a suspect in Simon's murder—Knox Myers—Maeve's friend and ex-boyfriend, as well as an intern at the law firm Until Proven—and Phoebe Lawton—a waitress at a local café—are juniors at Bayview High.

At Until Proven, lawyer Eli Kleinfelter, who is engaged to Ashton Prentiss—sister of Addy Prentiss, another suspect in Simon's murder—has been receiving death threats.

One day, the students receive a message from an anonymous texter they call "the Unknown", who invites them to play a game of truth or dare.

Brandon, another Bayview High student, dies after jumping off a faulty landing,[a] which Maeve, Knox, and Phoebe later find was a dare.

Emma maintains that she did not text him again; she and Phoebe notice a writing style similar to their little brother Owen's, but do not reveal anything to the police.

[4] The novel formed the basis for the eight-episode second season of the teen drama mystery television series One of Us Is Lying, which was released to the streaming service Peacock on October 7, 2021.