Greg Sanderson is helping his wife, Jan, to recover from a nervous breakdown and revive their strained marriage. Their privacy is interrupted by the arrival of Greg's stunning and mysterious sister, Laura. Jan's paranoia deepens as she suspects that Greg's and her sister's relationship is too close. In her desperation, she confides her fears to the landlord but his weird reaction only creates more confusion.
In 1970, three children are born at the height of a total eclipse. Due to the sun and moon blocking Saturn, which controls emotions, they have become heartless killers ten years later, and are able to escape detection because of their youthful and innocent facades. A boy and his teenage sister become endangered when they stumble onto the bloody truth.
