The Phantom of the Monastery by Fernando de Fuentes

6.14

Alfonso, Eduardo and Cristina get lost when visiting a forest. A strange monk finds them and takes them to an ancient convent. There, the three amigos suffer personality changes, specially Cristina who tries to seduce Alfonso in a strange coincidence to a story told by an old monk. After some efforts to escape, Alfonso is trapped inside a jail and more strange and macabre situations happen.