Like all teenagers, Sagesse is wry, introspective, self-obsessed. But when her family is brought to the brink of destruction by a single wild act - her grandfather takes a potshot at one of her chic young Parisian friends by the swimming pool, to be precise - it propels her into the process of weighing, prioritising and judging that is known, eventually, as adulthood. Like a shadow that ripples every so often across the surface of the water, the family's Algerian background haunts the characters and the story, a mystery that is, despite the novel's resolutely honourable ending, never quite solved. Messud quotes St Augustine by way of a prelude - "a heart that understands cuts like rust in bones" - and there could be no more succinct summing-up of her calm, detached, precise prose.