Emily Stewart is the girl who claims to stand between the living and the dead. During the quiet summer of 1925, she and her brother, Michael, are thirteen-year-old twins-privileged, precocious, wandering aimlessly around their family's estate. One day, Emily discovers that she can secretly crack her ankle in such a way that a sound appears to burst through the stillness of midair. Emily and Michael gather the neighborhood children to fool them with these "spirit knockings." Soon, however, this game of contacting the dead creeps into a world of adults still reeling from World War I. When the twins find themselves dabbling in the uncertain territory of human grief and family secrets, everything spins wildly out of control.