It happened on a tree-lined street in Notting Hill to a woman who seemed to have the perfect life. Ellie Lerner's best friend, Lucy, was murdered in front of her young daughter. And, as best friends do, Ellie dropped everything - her marriage, her job, her life in the Boston suburbs - to travel to London and pick up the pieces of Lucy's life. While Lucy's husband, Greg, copes with his grief by retreating into himself, eight-year-old Sophie has simply stopped speaking.

Desperate to help Sophie, Ellie turns to a book that gave her comfort as a child, The Secret Garden. The two spend hours exploring the novel's winding passageways, its story of hurt, magic, and healing blooms around them.

But secrets emerge - some big, some small - secrets Lucy kept hidden, even from her best friend. Over a summer in London, as Ellie peels back the layers of her friend's life, she's forced to confront her own as well: the marriage she left behind, the loss she'd hoped to escape. And suddenly Ellie's carefully constructed existence is spinning out of control in a chain of events that will transform her life - and those around her - forever.