We begin The Man in the Iron Mask with the description of an altered friendship. Baisemeaux is the man in charge of the Bastille (that would be the famous French prison).
He and Aramis had always been friends, but ever since Aramis was promoted to hearing confession, the dynamics of their friendship has changed.
Aramis is now in a superior position.
Baisemeaux leads Aramis to a prison cell, and is then dismissed.
The prisoner is a discouraged young man, and makes no move to acknowledge Aramis's presence.
Aramis asks the man if he wanted a confessor.
The young man says yes, then changes his mind once he takes a good look at Aramis.
Aramis looks at the prisoner and is struck by the man's "easy majesty."
Aramis asks the obvious question – doesn't the prisoner want to be free?
The two discuss the meaning of liberty: the prisoner thinks he's free; Aramis says he isn't.
Aramis asks the prisoner about the crimes he has committed. The prisoner replies that he tries not to think too deeply about his situation, otherwise he will go mad.
Meanwhile, Aramis has been hinting that he has a revelation for the prisoner. Fed up, the prisoner finally tells Aramis that the two of them can reveal their thoughts at the same time.
Aramis argues that the prisoner has lied about his childhood.
The two of them finally agree that the prisoner distrusts Aramis.
Aramis tells the prisoner that the two of them are actually old friends. They met once in a village called Noisy-le-Sec.
The prisoner promises to listen to the revelations Aramis has in store, but first wants to know how and when the two of them met.
It turns out that "fifteen or eighteen years ago" Aramis accompanied a lady in black silk to visit the prisoner.
The prisoner learns that Aramis was called the Abbé de Herblay, and that he was one of the King's Musketeers.
Aramis says that he is the same man.
The prisoner admits to having recognized Aramis.
Aramis tells the prisoner that if the King were to learn of his visit, he would have Aramis killed.
Gaining some confidence, the prisoner explains that the lady in black silk visited him on two other occasions with another person.
Aramis asks if the prisoner knew the woman's identity. The prisoner replies that she was a lady of the court.
The prisoner tells Aramis that he saw the woman with a man in his mid-forties and also with another lady of the court.
Aramis asks if he was always in prison.
The prisoner replies that he was once held under strict house arrest. He asks Aramis to explain the whole situation to him, starting with the identity of his tutor (that would be the man in his mid-forties).
Aramis says that the tutor was a good man who was compelled to lie to the prisoner about his parents. Although the young man's father is dead, his mother is still very much alive.
The prisoner asks if his presence in the world would lead to the unveiling of a great secret.
Aramis answers in the affirmative.
The prisoner speculates that whoever put him in prison must be powerful.
Aramis hesitates before again answering in the affirmative.
The prisoner speculates that his nurse and tutor must have been in great danger. Aramis tells the young man that they were poisoned.
About eight years ago, the prisoner says, he was living in his house when he went to take a nap after a fencing lesson.
The tutor suddenly yelled from an upper story, calling for the young man's nurse, Perronnette.
The tutor had received a letter from the Queen, but as soon as he opened it up, it drifted out the window and fell down the well.
The nurse and the tutor decided that they must get a young man from the village to go down the well and fetch the letter.
As soon as they leave, the prisoner went down the well and grabbed the Queen's letter himself. This secret letter tells him that both his tutor and nurse are of high rank.
Eventually he confessed his actions to the tutor and the nurse. He was afterwards moved to the Bastille, and never saw his attendants again.
Now it's Aramis's turn to tell a story.
Aramis gives a bit of a history lesson. France has been ruled by King Francis I, King Henry IV, and most recently, King Louis XIII, who was a weak monarch and let Cardinal Richelieu do most of the actual governing.
King Louis XIII was married to Anne of Austria, who had difficulty producing an heir, until she produced twin boys. That, apparently, is the big secret.
King Louis XIII decided not to reveal the existence of the younger twin.
Eventually, King Louis XIII dies and is replaced by King Louis XIV.
Aramis then hands the prisoner a portrait of the current king (that would be Louis XIV) and a mirror, asking the prisoner to compare the two.
The prisoner is shocked to see the similarity. He insists on being allowed to remain in the Bastille. He asks Aramis not to make any promises he cannot deliver.
Aramis is, however, bent on putting the prisoner on the throne of France.
Before he leaves, Aramis kneels and kisses the prisoner's hand in homage.
Aramis raps on the door and Baisemeaux opens it and guides the confessor out of the prison.