Mary Lennox didn't think about death until the day it knocked politely on her bedroom door and invited itself in. When a terrible accident leaves her orphaned at fifteen, she is sent to the wilderness of the Georgian Bay to live with an uncle she's never met. At first the impassive, calculating girl believes this new manor will be just like the one she left in Toronto: cold, isolating, and anything but cheerful, where staff is treated as staff and never like family. But as she slowly allows her heart to open like the first blooms of spring, Mary comes to find that this strange place and its strange people--most of whom are Indigenous self-named "halfbreeds"--may be what she can finally call home. Then one night Mary discovers Olive, her cousin who has been hidden away in an attic room for years due to a "nervous condition." The girls become fast friends, and Mary wonders why this big-hearted girl is being kept out of sight and fed medicine that only makes her feel sicker. When Olive's domineering stepmother returns to the manor, it soon becomes clear that something sinister is going on. With the help of a charming, intoxicatingly vivacious Metis girl named Sophie, Mary begins digging further into family secrets both wonderful and horrifying to figure out how to free Olive. And some of the answers may lie within the walls of a hidden, overgrown and long-forgotten garden the girls stumble upon while wandering the wilds ...