Helen's idyllic life, handsome architect husband, gorgeous Victorian house, and cherished baby on the way, begins to change the day she attends her first prenatal class and meets Rachel, an unpredictable single mother-to-be. Rachel doesn't seem very maternal: she smokes, drinks, and professes little interest in parenthood. Still, Helen is drawn to her. Maybe Rachel just needs a friend. But her increasingly erratic behavior is unsettling. And Helen's not the only one who's noticed. Her friends and family begin to suspect that her strange new friend may be linked to their shared history in unexpected ways. When Rachel threatens to expose a past crime that could destroy all of their lives, it becomes clear that there are more than a few secrets laying beneath the broad-leaved trees and warm lamplight of Greenwich Park.