The Catholic Church and its upper echelons remain an organization shadowed in mystery centuries after its founding, which makes its inner workings excellent fodder for a thriller.

When the Pope dies following a brief illness, it intensifies Father Lawrence's (Ralph Fiennes) crisis of faith as he must oversee the vote for the church's next leader. The cardinals converge on the Vatican — hence the film's title, Conclave — to wage a war for the church's soul as the conservative and liberal factions vie for control. As the vote goes on, secrets are exposed, and the ambitious, power-hungry cardinals eat each other tail-in-mouth ouroboros style.

Will the next Pope be the traditionalist Tedesco (Sergio Castellitto), the progressive Aldo Bellini (Stanley Tucci), the smug Cardinal Adeyemi (Lucian Msamati), or the reluctant Lawrence himself who is keen on resigning his post when all this is done? Director Edward Berger keeps us guessing, ratcheting up the tension as each new twist snowballs on top of the last.

Ralph Fiennes in 'Conclave'.

Focus Features

Fiennes anchors the thriller, bringing an elegant world-weariness to a man wrestling with the institution and its faults. He advocates for doubt over certainty and preaches the importance of a diversity of expression and acceptance of faiths. "Faith is a living thing because it walks hand in hand with doubt. With certainty, there is no need of faith," he preaches. "Let us choose a Pope who doubts." As he tries to ensure the church is not dragged backward and that the next Pope is not dogged by corruption or scandal, Fiennes gives Father Lawrence a nobility of spirit while still making space for human fallibility. His constant inner war between following the rules and doing what is right is writ across every hard-won line on his fame.

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Berger shoots the film with an elegiac style that utilizes the stark black and white marble and Renaissance architecture to great emotional impact. The cardinals' black and white umbrellas contrast with the velvet reds of their caps and sashes, emphasizing the pomp and solemnity of their purpose, while also reinforcing an air of mystery.

Ralph Fiennes and Stanley Tucci in 'Conclave'.

Courtesy of Focus Features

Fiennes is backed by a stellar supporting cast that, in addition to Tucci's firebrand Bellini, included John Lithgow as a sanctimonious curate and Carlos Diehz as Cardinal Benitez, intriguing and comforting in his calm stillness.

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Isabella Rossellini also steals scenes as a nun, Sister Agnes, who can't help interject herself in the name of justice. Clad in a habit, a costume not unlike the one her mother wore in The Bells of St. Mary's, she evokes Ingrid Bergman's unique blend of classical rectitude and iconoclasm in such a way that it almost feels like you are watching a ghost.

Isabella Rossellini in 'Conclave'.

Courtesy of Focus Features

Conclave is packed with unexpected twists and its final reveal is one viewers will never see coming, an increasingly rare occurrence in modern movie-making and the mark of an impeccably crafted thriller. Much of the film interrogates the gap between the Catholic Church's sins and the true meaning of faith — but nothing does it more so than this final surprise which seeks to see us all as the creatures that God made us, existing in the space between the world's certainties. It champions a church that sees all beings as worthy of God's love, no matter our creed or custom. All the while still leaving room for doubt, for without it there is no need for faith. Grade: A-