4 ideas
The literature student Puck Ekstedt, whose fiancé Einar Bure is among the group, narrates the case. It is solved by Christer Wijk, a police detective with ties to the circle, who uncovers the concealed relationships behind the death and becomes the recurring detective of Maria Lang's series.
A murder inside a small, bounded group of friends makes every suspect someone the others believed they knew. The investigation therefore works as a forced audit of intimacy. Each person's alibi depends on what the others are willing to admit about where they were and with whom. Solving the crime means breaking the group's collective discretion, not finding a stranger.
The title's premise is that a killer is never the only liar. Innocent people hide affairs, attractions and sexual secrets that respectable small-town society would punish, and their evasions obscure the real crime. Shame about desire, more than guilt about violence, generates most of the deception the detective must strip away.
Telling the mystery through a participant like Puck, who is emotionally tied to the suspects, turns her loyalties and blind spots into part of the puzzle. The reader sees what a friend would notice and misses what a friend would refuse to suspect. This shows how closeness distorts judgment in the very situations where closeness supplies the most information.