"Reign" Episode 11, "Inquisition," is about Queen Catherine's past and her ploys. The episode begins with Mary and Bash finding out that the pagan mark has not disappeared from the baby's foot. A guard informs them that the King has returned to the castle. Queen Catherine's family visits her, bringing with them good as well as bad news. King Henry was unable to meet the Pope because of the family's influence, which means Bash cannot be immediately announced the heir to the throne of France. However, the King intends to execute the Queen by sticking the adultery charges on her. King's old friend, Richard Delacroix, is introduced. He holds a grudge against the Queen, as he blames her for his exile. Richard does not hide his happiness at the thought of Queen getting killed. Richard is helping King Henry to polish Kenna's testimony against the Queen. The Queen comes to know that Richard will be in charge of the evidence against her.

Nostradamus has been incarcerated. The King intends to present him as the Queen's lover. Queen Catherine believes that by destroying Bash, she can escape death. She comes to know about Bash and Mary's visit to the wine cellar to see a baby. Queen Catherine walks in when Mary and Bash are sending-off the baby, with the wet nurse's mother. The plan is to send the baby to the convent.

Queen Catherine notices the pagan mark. She warns Mary about the consequences of Bash's link to Pagans. Mary might very well end-up on Bash's adjacent stake, Queen threatens her. Mary isn't the one to plead. She tells the Queen that Bash will be at her side when the Queen is executed.

Queen plans to use Bash's Pagan history to destroy him. She visits Nostradamus in the prison to know about Bash's connection with heretics in the blood woods. Nostradamus believes that Bash might have seen things in the blood woods while on his hunting missions. The King walks in with an offer. He is ready to spare Nostradamus' life in exchange for testifying against Catherine. Nostradamus refuses the offer.

Catherine confronts the wet nurse, asking her to tell the whereabouts of the baby. Her men have found out that the baby is not at the convent. She uses her family members to get the information out of the wet nurse. The baby is at wet nurse's mother place. Bash and Mary are told that the Queen and her men know about the baby's location. They try to reach the place before the Queen's men.

Clarissa comes to the Queen's room and tries to scare her off. The Queen realises that the castle ghost is a living being. She demands to know the truth from Nostradamus and why he had lied to her. Nostradamus tells her that he felt responsible for the girl. Clarissa was born with an ugly scar on her face and Nostradamus' father had brought her home as a new born child. The father had tried to remove the scar, surgically, at first. Later, potions were used, which deformed the baby. She was given-away to a couple but her deformity made everyone believe that she was the devil's child. Nostradamus brought the tormented Clarissa to the castle to atone his family's sins against her. The Queen looks affected by what Nostradamus is saying.

Bash and Mary reach the wet nurse's place before Queen's men. However, they did not reach early enough. The Queen's men reach the place before the two could take the baby and the wet nurse's family to some place safe. Bash and Mary are hiding in a closet when Queen's men come knocking. They are unable to find Bash and Mary. However, they take the baby with them.

Queen Catherine meets the King. They recall the brimming with love, initial days of their marriage. She did not give birth to a child for ten years, and her infertility scared her. The King tells her that he would have not executed her for not bearing a child. The reminiscing of the naive days make the two kiss each other, which leads to the bed. The two seems to have reconciled, as the King postpones the date of testimony against Catherine.

Richard informs the Queen about the dismissal of the witnesses' testimony against her. It is revealed that the two have been lovers for years. They passionately hug and profess their love for each other. The fear of their romantic relationship getting revealed had made Richard take the exile route.

The Queen's men visit Catherine, with the baby. However, the baby does not have the pagan mark. The wet nurse's mother tell Mary and Bash about Queen Catherine giving birth to a child, with a scar on her face. She also tells them that the child might have been the lover's child, and not King Henry's. Mary and Bash take her to the King and she tells him, everything. The King figures out that the baby must have been of Richard, as that kind of mark runs his family. He confronts him and sentences him to death.

Queen Catherine pulls out the last trick to save herself. She shows a pagan ball to King Henry and tells him about Diane's being a pagan. The Queen tells the King that the guard saw her find the pagan ball from Diane's drawer. When the King kills one of the guards, the second guard declares that he did not witness anything. The King reveals to the Queen that he knew about Diane's past, as she told him about it. To Bash, the King tells that one should cut any threat like a weed.

The Queen's family washes their hands off her after they come to know about her lover. They present her poison to kill herself, and not suffer a crueller death. Mary tells Bash that her heart is open and kisses him. She does not expect him to be Francis, and conveys the same to him. Bash promises to cut down anyone or anything that harms Mary.

Mary is taking a bath in the tub. Queen Catherine arrives to drop the poison dust in the tub. She has also consumed the poison. She puts a knife at Mary's neck so that she does not escape. However, Clarissa pushes down Catherine and pulls-up Mary. She makes sound to inform the guards. Clarissa calls Catherine mother but the Queen does not respond, favourably.

Bash arrives right on time and holds Mary, wrapping her in a towel. Queen Catherine warns Mary about her choice, while Mary tells her that Bash and she just killed the Queen of France.