While trying to enjoy a peaceful Halloween with his mother, Linda Garner Tim is paid a visit by his rambunctious, up-for-anything friends. After reluctantly letting them inside the house, he becomes intertwined with the circumstances of their Halloween pranking. One, it turns out that that has broken a sacred tradition between humans and otherworldly deities known as the Aos Si. A call back to terrors birthed in the mythology, lore and atmospheric dread behind the Halloween traditions based in an ancient Celtic past.