Michigan witnesses a bloody and terrifying crime involving a dysfunctional family who have just moved from Tomelloso (Ciudad Real) hoping for a fresh start. But instead of peace, they find even greater family chaos and a two-legged horse stalking their new home.
After 30 years without any progress from the authorities, a detective agency sets out to unravel the Mascamierdas case: a twisted serial killer who inexplicably ends entire families every December 13th.
