The Day of the Beast

A Basque priest Ángel Berriatúa confesses to another priest that he intends to commit as much evil as he can. The other priest is shocked until Ángel whispers his reasons, and the confession becomes a pact. When the other priest agrees to help him, a large cross falls from an unseen support and crushes him.

Ángel ventures into downtown Madrid, deliberately sowing chaos. He steals from the homeless, shoves a street performer, and insults a dying man by telling him to go to Hell while taking his wallet.

In a record store, Ángel meets José María, a self-described Satanist and heavy metal fan from Carabanchel. José María gives him a tape of what he calls the most evil band and shelters him at his mother's boarding house.

Ángel moves into José María's mother's boarding house, sharing space with José María's mother, grandfather, and Mina, a woman he is attracted to who helps with the business. The new living arrangement marks the start of their collaboration.

Ángel tries to steal a book by occult TV host Professor Cavan, believing it will reveal how to sell his soul to Satan. He fixes on a secret Bible code about the Antichrist being born at midnight on Christmas Eve, which drives his risky pursuit.

Ángel and José María kidnap Cavan and torture him to learn how to complete the ritual. They aim to obtain a virgin's blood, starting with Susana, Cavan's girlfriend, but discover she is not a virgin after knocking her out.

Ángel returns to the boarding house to grab Mina's blood, but José María's mother objects and tries to shoot him. Ángel escapes with blood but accidentally kills José María's mother in the chaos.

They burn the paper scraps, take LSD, and perform what Cavan calls a ritual. A he-goat appears briefly, and the devil taunts Ángel from the burnt pages, showing that the attempt to bargain with darkness was ultimately a failure.

The police arrive on suspicion of Cavan's kidnapping, forcing the trio to flee the apartment. They scatter into Madrid streets, unsure of what to do next as the search intensifies.

Ángel and José María drive through Madrid seeking any sign that could reveal the Antichrist's birth. They chase a man giving a Nostradamus lecture, leading to a stunt-filled chase where three men dressed as the Three Wise Men are shot by police.

Desperate, they crash a heavy metal show and are beaten by attendees. Later, Cavan goes on television to appeal to Ángel, claiming he now believes Ángel's theory and urging him to call.

Cavan points out the devil's symbols, guiding them to the Gate of Europe towers where an extreme-right gang has murdered homeless people and sprayed Limpia Madrid. The gang's leader is revealed as the devil when he throws José María from the building; Ángel then kills the gang and shoots the devil.

Sometime later, another actor takes over Cavan's TV show, and Ángel and Cavan become homeless drifters. They reflect on their actions and the impossibility of fully revealing their deeds.

Ángel misses José María but has come to accept the duo's fate, recognizing their bond and the world they helped save in their own strange way. The ending leaves them wandering, not sure what comes next.