Callie Roberts is a divorced, unemployed, single mother who lives in a rented flat in central London. Her American best friend, Suzy Howard, has come to London from Colorado to live with her husband, Jez. Upwardly mobile, Suzy and Jez have three kids and lead a great lifestyle, at least in Callie’s eyes. On a hazy, summer day, the two women swim in the pools of Hampstead Heath, neither friend very far away from the other.

As Callie watches her young daughter, Rae, she thinks about the value of Suzy and the constant stinging rejection she gets from the other mothers who can afford to place their kids into the oversubscribed, posh local primary school. What begins as a solid friendship soon turns to resentment when emotionally fragile Debs Ribwell moves next door. One of the organizers of the after-school club, Debs hides a shameful past which leads her husband to conclude that “it's not really a good idea for you to be working with children again at all.”

Telling a dark, edgy story of suburban paranoia and manipulation, Millar alternates between Callie, Suzy and Debs's effusive narratives. She takes her characters seriously, considering their struggles from moral, ethical, and humanistic perspectives. Callie’s ex-husband, Tom, a globe-trotting photographer, still holds a kindly if tedious grudge and a stunted animosity towards Callie. When Callie actually considers returning to work, Tom can’t quite believe that her priorities would get in the way of Rae, whose heart condition has sucked them dry both emotionally and financially.

Callie continues to beat herself up, wondering why she’s so unpopular with the school mothers (for reasons she’s given up trying to understand) while Suzy and Jez fight back humiliation, their dark marriage playing out behind closed doors. Suzy sees the “blackness” in Jez’s eyes; she can’t quite believe his blind resistance to having more kids. Aching for a connection, she realizes that Jez is far from the man she made love to that pristine day at the lake in Colorado.

As Callie’s flat becomes a place of no light, a place of secrets where “lies are locked away at night,” Millar’s shifting narrative helps create suspense, making us question her characters’ reliability. An accident with Rae causes a fissure to open up with Suzy, who up until now has attempted to balance her fragile life of motherhood, far from the "liars and betrayers, users and demons of home." For a woman who once saw London as a fresh start, Suzy now seems unable to cope with a lonely marriage to a husband she cannot understand but cannot yet abandon.

Callie and Debs struggle too. Callie loves Rae but feels guilty for betraying her position of motherly trust when she goes to work as a sound technician for a successful media company. Always struggling, Callie seeks calm in the storm of neighborhood loneliness, while Debs is increasingly paranoid, haunted by noises and visions from next door. Debs clearly needs nurture, but she’s set adrift after her acrimonious past, a tool used by the neighborhood parents to injure her. Then there are Suzy’s vague memories that surface in the form of nightmares and turn on a series of actions that terrify Debs into submission.

The book is made up of images, moments in time, the stages in Callie, Debs and Suzy’s relationships, becoming oblique encounters bereft of the usual machinery connecting each to the other when so much is eventually revealed. By novel’s end, Suzy’s escapades breed more violence and upheaval, leaving Callie to repair the broken pieces of her life, hopefully with her ex-husband’s patient assistance.