The film follows the true-life story of Father Stuart Long, a boxer-turned-priest who inspired countless people during his journey from self-destruction to redemption. According to Wahlberg, “he was a very tough guy who was a fighter, a football player…anything but a spiritual guy. He found his calling, and decided, after falling in love with a woman, that he wanted to become a priest. He suffered from this horrible muscular degenerative disease but was still ordained as a priest and passed away, but not before he was able to inspire thousands upon thousands of people.”
Father Stu suffered from inclusion body myositis, an autoimmune condition characterized by progressive muscle inflammation, weakness, and atrophy (muscle wasting). Inclusion body myositis (IBM) is the most common acquired myopathy in those age 50 and older.