Content Warning: This section of the guide contains references to child sexual abuse, pregnancy loss, self-harm, and suicide. In addition, the source text uses offensive and outdated terms for sexually active women, which are replicated only in direct quotes in this guide.

Ella Longfield tells the reader she made a mistake, though she does not specify her error. She asks the reader if they would have behaved any differently in the circumstances she is going to recount.

In a flashback to July 2015, Ella, a florist from Devon, is on the train to London, pretending to read a book instead of the magazine she’d really wanted, to appear intellectual. Consequently, she is bored and her attention wanders to the other passengers. She watches a couple of boisterous young men get in, carrying large black garbage bags. When the men spot two beautiful 16-year-old girls a few rows away, they move toward them. Soon, the four are chatting loudly. The girls, Anna and Sarah, tell the men, Karl and Antony, that they are on their first solo visit to London to celebrate the end of GSCEs (secondary school exams, typically taken at the end of Grade 10 or 11).