Twins Hunter and Mercy Goode are witches, direct descendants of Sarah Goode, the founder of the town and first protector of Goodeville. As their ancestors have done before them, it is now time for Hunter and Mercy to learn the ropes of what it means to be the Gatekeepers - the protectors of the Gates to different underworlds, ancient portals between their world and worlds where mythology rules and nightmare is a reality. When their mother becomes the first victim in a string of murders, their lives feel shattered. The sisters are forced into action and uncover much more than the perpetrator: something has gone wrong with the sealed Gates. They are now opening. Ancient mythological monsters are free and infecting the quiet town of Goodeville. Will Hunter and Mercy accept their destiny as Gatekeepers and battle to rid their world of creatures without one of them paying the ultimate price?