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 13-year-old twins—privileged, precocious,
wandering aimlessly around their family's estate. One day,
Emily discovers she can secretly crack her ankle in such a
way that a sound appears to burst through the stillness of
midair. Knock, knock . . . 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—knock,
knock—very thing spins wildly out of control.