Tim's mother has brain cancer, but his friends steal a sack unleashing the Aos Si Celtic spirit on Halloween night. They must survive the night or sacrifice their lives to the spirit. The spirit pursues them for their trespass.

Halloween was always Tim's favorite holiday-until his mother was diagnosed with brain cancer. Now, all he wants is a quiet night in. That is quickly disrupted when his friends pay him an unwanted visit after stealing a mysterious sack from the doorstep of a local crazy. This sacrilegious act unleashes the Aos Si, a Celtic spirit that walks the Earth on Halloween. They must band together and survive the night or make the ultimate offering-their lives. This Halloween, all who trick are treats.