The penultimate episode of "Reign" showed a mad King Henry thinking of killing his own son Francis and marrying his widow Mary, so that he could claim the throne of England. In the finale episode, titled "Slaughter of Innocence," the King's madness will reach a fevered pitch, which will lead to more cruelty from his side. According to The CW's synopsis of the final episode of "Reign," this will prompt Mary and Francis to take some drastic, brutal action, which will change the fate of France.
The title "Slaughter of Innocence" alludes to Mary emerging as a determined, calculated Queen of Scotland. She will no longer be the innocent Mary. In the preview clip of the final episode, Queen Catherine can be seen telling Mary, "I miss the girl you were." Mary can be seen wearing her Queen of Scot's crown and sitting beside King Henry. Duke of Guise can be seen suggesting to Mary to strike first and take control of the kingdom, and "make yourself the most powerful person in France."
In the previous episode, Bash and Nostradamus set out to decimate the Darkness in the wood. The synopsis of the episode reveal that this "unforeseen terror" could cost Mary and Francis, and their friends, everything.
As reported previously, Lola will be giving birth to a child this season only. The synopsis of the episode suggests that she will be seen going through a life-threatening labour at a place outside the castle. It is expected that Mary will be making a bold choice when she will come to know about that.
Official Synopsis of "Reign" Season 1 Finale, Episode 22, "Slaughter of Innocence": "In the first-season finale, Mary and Francis take drastic action in response to Henry's madness. Meanwhile, a terror in the woods puts everyone in peril; and Mary makes a bold choice when she discovers Lola is in the midst of a life-threatening labour."
David Frazee has directed the episode, while Laurie McCarthy and Doris Egan have written it.
"Reign" has already been renewed for Season 2.