Always think in threes and you'll never fall, Cora's father told her when she was a little girl. Two feet, one hand. Two hands, one foot. That was all Cora needed to know to climb the trees of Brooklyn. But now Cora is a middle schooler, a big sister, and homeless. Her mother is trying to hold the family together after her father's death, and Cora must look after her sister, Adare, who's just different, their mother insists. Quick to smile, Adare hates wearing shoes, rarely speaks, and appears untroubled by the question Cora can't help but ask: How will she find a place to call home? After their room at the shelter is ransacked, Cora's mother looks to an old friend for help, and Cora finally finds what she has been looking for: Ailanthus altissima, the "tree of heaven," which can grow in even the worst conditions. It sets her on a path to discover a deeper truth about where she really belongs.