Father Frank Dempsey is a Roman Catholic priest who harbours an almighty secret: he doesn't believe in God. Despite this, or maybe because of it, he is brilliant and hugely successful as a priest. His unconventional methods, which include driving a taxi to raise funds, bring his flock together and transform what was once a drab North London parish. It's all going beautifully until Sarah Marshall hops into his taxi and into his life, slowly putting his vows under incredible strain.