People are always surprised to learn about the close relationship between Beatrice Hemming and her younger sister, Tess. After all, the age difference between them is five years --- too far apart to be true friends, right? What outsiders fail to understand, however, is the intensity of a sister relationship that grows only closer after tragedy. For there was a middle child --- a brother, Leo --- who had cystic fibrosis and died when he was still young. His illness and death, and their father's near-simultaneous disappearance from their lives, have left Bee and Tess an island of two survivors.

Rosamund Lupton's debut novel is a winner, as worth reading for its psychological intensity as it is for its mystery plot, not to mention the genuinely surprising twist near the end.

They're adults now, in their 20s, with an ocean separating them. Beatrice has chosen a designer life in New York City, where she's a graphic designer for corporate clients. Tess also has artistic talent, but of a very different kind. A promising art student, she's selected a bohemian lifestyle in London rather than the glossy trappings Bee favors. Tess lives in a basement flat, wears hand-me-down clothes --- and is expecting a baby whose father is her (married) art school tutor.

When Bee gets a call from her mother that Tess has been missing for several days, she immediately leaves for the UK, bringing her suitable but not-quite-perfect fiancé along for the trip. While they're there, Bee reconnects with her fragile mother even as she neglects all other relationships in favor of investigating Tess's mysterious disappearance. As she uncovers more and more perplexing details, Bee begins to ask herself questions, too: How well did she really know her sister? And how much might she be at fault for what may have happened to her?

"I'd do anything to have a second chance, Tess," Bee thinks to herself in a moment of mixed-up grief and guilt. "But unlike our storybooks, there's no flying back past the second star to the right and through the open window...I can't sail back through the weeks and in and out of the days returning to my bedroom where my supper is warm and waiting for me and I'm forgiven. There is no new beginning. No second chance. You turned to me and I wasn't there."

Bee's sorrow and guilt compound themselves into a bizarre blend of reactions. She finds herself identifying, sometimes chillingly so, with her younger sister, even as she doggedly insists that the police investigators listen to her version of events, a story they've all but discounted.

Rosamund Lupton's debut novel is a winner, as worth reading for its psychological intensity as it is for its mystery plot, not to mention the genuinely surprising twist near the end. At times, Bee's outpourings of affection toward Tess can seem melodramatic or old-fashioned, but as the reader grows to understand the true stakes of Bee's story, her emotional involvement becomes both more convincing and truly poignant. "We are conjoined by hundreds of thousands of memories that silt down into you and stop being memories and become a part of what you are," Bee considers, as she approaches a moment of utter, heartbreaking empathy that will arouse readers' emotions as well.