Every October 31 pint-sized ghouls and goblins wander through neighborhoods knocking on doors and asking for treats . . . little do they know they're actually carrying out an ancient tradition dating back thousands of years. Discover how the "trick-or-treat" custom originated during the harvest festivals in ancient Ireland when food and sweets were used to coax the dead into remaining in the spirit world. Learn how Christianity tried to co-opt the celebration by turning it into All Saints Day but how the underlying--and sometimes controversial--dark elements of the holiday have survived.