Holly takes the card to Detective Stephen Moran of the cold case squad who arranges to investigate with Detective Antoinette Conroy of the murder squad. The main 'suspects' for who placed the card on the bulletin board are two groups of friends. One group contains 'the snobby girls', who think it's their right to date the most desirable boys from St. Colm's. The other group contains 'the nice girls' who make an oath to stick together and forsake boyfriends from St. Colm's - who they consider a bad lot who take advantage of girls and blab about it.
The book is told in alternating scenes: in the present, the detectives repeatedly question the girls to find out what they know; in flashbacks we see the interactions among the teen girls and boys from the private schools: posturing at the local shopping mall; budding romance at the St. Valentine's dance; sneaking out of school to meet up; secret phones for texting; etc. I have to admit I was entertained (and sometimes annoyed) by the lingo the girls use when they speak to each other and to the detectives. Sassy, fun, sometimes mean - and almost always disrespectful to adults.
Of course it's impossible for teen girls to ignore nearby boys - no matter what they promise - and a number of relationships flourish and wane among the students of St. Kilda's and St. Colm's. Jealousies arise, people spy on each other, girls get protective, girls get furious, threats are made, and so on. Is this related to Chris's death? Well...yes.
I've enjoyed Tana French's previous books but this wasn't a favorite for me. The detective work, which consisted almost entirely of talking to the girls on the school grounds, became tedious. I would have liked more moving around and forensics. Also, I didn't especially like or care about the characters. The snobby girls were unbearable and even the nice girls weren't particularly sympathetic. I also thought these girls - 15 and 16 years old - seemed too young to engage in the level of devilry they got up to.
The resolution of the crime wasn't completely satisfactory either; I felt it didn't flow smoothly from the rest of the book. Nevertheless, I'd mildly recommend the book to fans of Tana French; as usual with her books, familiar characters from past books show up in current ones and it's good to see what's going on with them.