Are you ready to venture into the forbidden?

Sister Giunia (SONG Hye-kyo) is convinced that the evil spirit possessing Hee-joon (MOON Woo-jin) is one of the 12 Manifestations. With the exorcist priest unable to come in time and Hee-joon’s life clearly at risk, Sister Giunia decides to break a sacred rule: ‘An unordained nun cannot perform an exorcism.’

However, Father Paolo (LEE Jin-uk), Hee-joon’s attending physician, firmly believes that only medicine can save the boy. When Sister Giunia discovers a secret about Father Paolo’s disciple, Sister Michela (JEON Yeo-been), she recklessly seeks her help to smuggle Hee-joon out of the hospital. Despite clashing with the fearless Giunia, Michela, feeling a connection to the boy, decides to join forces.

Together, the two nuns embark on a dangerous ritual, determined to save the boy at all costs, no matter the risks or consequences.

There’s only one rule: Save him at all costs!