The Witch of Blacklion follows the lives of two couples in a small Irish community in 1915. Rory and Mazey have a happy life raising their five-year-old son and helping out the town with their lush garden. A trauma causes Mazey to pull away from Rory and find solace in her painting. Richard is the new doctor in town who is immediately mesmerized by a reporter named Laura. Their happiness is short lived when Laura and her mother survive after the ship they were journeying on sinks. She claims an angel saved her life, and becomes obsessed with proving his existence while digging for proof that local healer Old Shelley is a witch. The perfect lives of the two main couples are disrupted by a series of tragic events. Laura and Mazey each suffer through a trauma that changes their lives and sends them both on obsessive missions. Love and romance blossom, however, and touch the lives of Old Shelley the shape shifter and Mordecai, the guardian angel.