Since I do not have access to the Spanish original, the following summary of The Purgatory of Saint Patrick is based on an English version presented online by Classical Authors. All direct quotations are taken from this version.
Philip de Roqui, a pirate, kidnapped Patrick and carried him off to sea. He planned to present him as a slave to King Egerius. However, as he neared his destination, God sent a sudden storm and sank his ship. St. Patrick and Luis Enius managed to reach land safely.
On shore, Patrick and Luis met King Egerius, his two daughters, and others. Patrick introduced himself, explained what had happened, and asked for help. In his introduction, he pointed out that he was a Christian and that God had given him the power to do several miracles.
King Egerius had been troubled by a dream in which fire issued forth from a slave and burned his two daughters to ashes. He feared that Patrick was the slave of whom he had dreamed.
Patrick confirmed his fears. He explained that the flame that issued from his mouth was the gospel that he was commanded to preach to the king’s subjects, his vassals, and his daughters, who would thereby become Christians.
When the king heard these words, he became angry. His daughter Lesbia defended Patrick. In contrast, Polonia, his other daughter, was unsympathetic.
Luis Enius then introduced himself. He identified himself as a Christian but pointed out that he was very different from Patrick. He had lived a shockingly sinful life, which he described in some detail. He acknowledged that Patrick had saved his life by pulling him from the sea after their ship had foundered.
The king honored Luis with his embrace. He allowed Patrick to live, but enslaved him. Patrick became the king’s herdsman. A peasant named Paul had the duty of guarding him.
Before Patrick and Luis went their separate ways, Patrick said: “Thou art a Christian; show thyself one in earnest.” Patrick wanted Luis to meet with him again sometime in the future. Luis promised to do so.
Polonia loved Philip de Roqui. To her delight, he did not die at sea.
An angel named Victor appeared to Patrick. The angel told him that he was supposed to go to France, become a monk, visit the pope in Rome, and return to Ireland as a missionary with the pope’s blessing.
The angel then told Patrick to come with him. The two disappeared.
For three years, Luis Enius had distinguished himself as a military leader in the service of King Egerius. Emboldened by his trophies, he attempted to win Polonia for himself. Polonia encouraged him.
They were surprised by Philip. During the ensuing argument, Philip insulted Luis. They drew swords and began to fight.
While they were fighting, the king arrived with soldiers. At the king’s command, they took Luis captive. Luis killed three men and wounded many others before he was subdued.
While these things were taking place, King Egerius was irritated because he had learned that Patrick had returned to Ireland and was converting many people to Christianity. For this reason, he commanded that Luis be executed, not because of anything that he had done, but because he was a Christian.
Polonia helped Luis escape. With singular ingratitude, he killed her. She called upon the God of the Christians before she died.
Luis wanted to leave the country. He got lost, so he forced Paul to guide him to the port. He planned to return to Ireland at a later date, so that he could punish Philip for insulting him.
Philip found the body of Polonia. While the king and others were mourning over her death, Patrick entered the scene.
In the ensuing conversation, Patrick told the king that Polonia’s soul still lived. When the king asked him to prove the truth of what he said, Patrick prayed to God. Then he raised Polonia from the dead.
Polonia was terrified by the secrets that had been imparted to her soul. She said that Christ was the true God, and she wanted to be baptized. Then she hurried away.
All who witnessed this miracle declared that Christ was the true God – all except the king. He thought that Patrick had practiced deceit. He suggested that Polonia had only been in a swoon.
To discredit Christianity, the king said that if Polonia had really died, her soul must have gone either to heaven or to hell. If she was in heaven, God was cruel to send her back to earth. If she was in hell, God was unjust if He gave a condemned sinner another chance at life.
Patrick replied that her soul did not go to either place, but remained in a sort of limbo, since God knew that she would soon return to her body. In addition, Patrick also told the king that there was a third place called purgatory, where souls were cleansed from stain before entering heaven.
The king demanded that Patrick prove that his words were true. In particular, he wanted Patrick to show him purgatory. Patrick was given an hour to satisfy the king. If he failed, he would die.
In response to Patrick’s prayers, an angel told him about a cave from which a contrite person could view purgatory, heaven, and hell. However, if anyone entered the cave without contrition, he would die and suffer woe.
Patrick led the king to the cave. They were accompanied by Philip, Lesbia, and others.
Polonia approached. She urged them not to enter the cave. While she was dead, she had witnessed its horrors.
Patrick acknowledged that this cave was not for those who felt no true repentance. However, whoever confessed his sins with a penitent heart would find forgiveness. In this cave, the penitent sinner would have his purgatory while still alive. [Calderón treated the sufferings in the purgatory of Saint Patrick as a penance with which a penitent sinner atoned for his sins. The concepts of penance and purgatory are doctrines of the Roman Catholic Church, to which Calderón belonged.]
Philip and others refused to enter the cave. The king called them cowards and boldly entered. He sank into the cave, amid flames and a lot of noise.
After leaving Ireland, Luis Enius traveled to England, Scotland, France, Italy, and Spain. He forced Paul to accompany him on all his journeys. Motivated by vengeance, he now returned to Ireland.
From the host of the inn in which they were staying, they learned that many changes had taken place since they had left. The host told them that the king was dead and Lesbia reigned in his stead. Moreover, many believed the gospel that Patrick preached, but Patrick himself had died during their absence.
On two successive nights, Luis lay in wait at the house of Philip. On each occasion, a muffled figure appeared and forced him to postpone his projected revenge. On the third night, the muffled figure addressed him. When Luis demanded that the stranger reveal his identity, he replied: “Follow me. Then you’ll know my name.”
Luis drew his sword and tried to kill the stranger. Since the muffled figure had no solid substance, the sword passed through him without wounding him. When the stranger left, Luis followed him and pulled off the sheet in which he was muffled. It was a skeleton.
The skeleton said: “Not know thyself? This is thy most faithful portrait; I, alas, am Luis Enius.” The skeleton then disappeared.
Luis now knew what kind of person he was. He was utterly horrified. He shed penitent tears and committed his soul to God, begging for mercy.
Luis heard celestial music and resolved to enter the purgatory of Patrick. He remembered that he had not yet fulfilled his promise to meet with Patrick again. He now resolved to meet Patrick in his purgatory.
The next scene showed what Polonia had been doing since the time when Patrick had raised her from the dead. She had been heir to her father’s throne, but she gave it up for the sake of the Lord. Instead of a royal palace, she lived in a lowly grotto.
As Luis was looking for the Patrick’s purgatory, he encountered a holy woman and asked for directions. It proved to be Polonia, and they eventually recognized each other.
When Polonia recognized the man who had murdered her, she struggled to suppress a desire for vengeance. When Luis beheld the embodiment of his greatest crime, he had to suppress the temptation to succumb to despair.
Polonia gave the penitent sinner the help he needed. Luis asked Polonia to pardon him. After receiving her assurance of forgiveness, Luis hurried away, filled with hope.
On the day when the trial of Luis was complete, Polonia led Lesbia, Philip, and others to the cave.
When Luis emerged from the cave, he asked Philip to pardon him. He also explained his experiences in the cave.
Shortly after entering, Luis found himself in an ornate hall, where twelve angels told him to trust in God in his immanent struggle with demons. They warned him that if the threats or the promises of the demons induced him to turn back, he would spend eternity in the lowest depths of hell.
Luis was then assailed by infernal visions. Disgusting forms attempted to drive him to despair. They urged him to return to earth. They buffeted him and bound his hands and his feet. They dragged him with sharp hooks and consigned him to flames.
Luis said: “O Jesus! Help me.” The demons fled, and the fires were extinguished.
Then they took him to a plain, where he heard cries of despair and bitter lamentations.
Luis saw the damned suffering different kinds of torments. For example, he saw a meadow in which the plants were flames. Many people were nailed to the ground. Vipers were gnawing the entrails of some of them, while others were repeatedly dismembered and reassembled.
Luis then beheld the people who suffered with smiles on their faces and hope in their hearts. Luis recognized that he was viewing the sufferings of purgatory.
The demons repeatedly attempted to subject Luis to the torments that he saw in his visions, but the name of Jesus protected him. Finally Luis had to pass over a river composed of melted sulfur. Those who fell into the stream were torn to pieces by serpents.
Invoking the name of God, Luis passed safely to the other side. He then passed through delightful woods and beheld a marvelous city in which angels and happy people lived. Here he saw Patrick, who was glad that Luis had kept his promise to see him again before he died.
The concept of a purgatory of Saint Patrick did not originate with Calderón. To learn what sources the dramatist used, consult the notes presented by Classical Authors.