As Reign Season 3 Episode 5 begins, Francis finds Mary praying. Mary is at peace with her mother's death because that means Francis gets to live.
Delphine doesn't want to stay at court. Bash wants her help capturing the murderer still at large. She agrees to stay and help when Bash tells her that their bond is greater than any binding ritual she may have performed.
Sir Nicholas expresses condolences for the death of Marie de Guise and tells Mary that Queen Elizabeth wants to make peace. Elizabeth will drop her attempts at conquest in Scotland if Elizabeth will sign away her claim to the English throne.
Francis finds Catherine in his private chambers having the room redecorated. Now that he is healthy once again, she wants the two of them to concentrate on producing an heir.
Francis uses his new lease on life to teach Mary how to sail on the boat he built during his sickness. He doesn't want her to abdicate her claim to the English throne but she believes it is a way to save both of their countries.
Nostradamus visits Catherine to tell her that the fight to become Regent may not be over and that Francis' life is still in danger. She wants Nostradamus to warn Francis but he believes it will be better received if the news comes from his mother. Mary and Francis sign Elizabeth's peace treaty and send Sir Nicholas back to England to procure Elizabeth's signature. Francis is called away by Catherine.
Catherine informs Francis of Nostradamus' prophecy and warns her son that he is still in danger. Something ominous remains his his future, so she begs him not to leave the castle. He refuses and whisks Mary away on a trip to Paris to celebrate his health and their life together. Catherine sees something concerning in their departure.
While on their journey to Paris, Francis bristles when Mary speaks of fate. To distract him, she suggests a detour.
Francis and Mary make love in the woods while Bash takes Delphine to investigate the site of the most recent murder. She feels rage and evil in a clearing and the two enter a barn where they find a secret room where the killer has jars of human hearts stored in vinegar on a shelf. While they're inside, the killer returns, but he manages to escape.
Mary returns to the carriage to retrieve lunch, leaving a mostly naked Francis behind to rest. On her walk, Mary is accosted by assassins. Francis goes in search of his wife and finds the tree from Nostradamus' prediction. He also finds Mary and begins fighting her attackers, killing one of them in the process before being injured by another. He is almost overcome by the assassins but manages to rally his strength and fight back, killing another. After the battle, Francis collapses.
Francis dies after telling Mary that he hopes she will learn to love again.
Catherine receives word from Bash that Francis has died in the woods on the way to Paris. She and an entourage of palace guards travel to the spot where Francis fell and find Mary by his side unable to leave. Catherine comforts her daughter-in-law as Bash and the guards carry Francis' body back to the castle. Nostradamus looks on as the pieces of his vision come together.
Mary visits Sir Nicholas believing Elizabeth is behind Francis' death. He assures her this is not the case, but she finds and burns the treaty anyway.
With Greer and Lola by her side, Mary attends Francis' funeral. Bash places Francis' crown and sword on his brother's coffin and takes a place beside Mary. Narcisse pays his respects and tells Mary that the assassins were Scottish Protestants who saw Marie de Guise' death as an opportunity to seize power. She knows Elizabeth was not behind the attack after all and orders the assassin hanged. Sir Nicholas begins plotting during Mary and France's moment of weakness.
Catherine invites Nostradamus to return to court to serve as her private counsel, but he refuses, offering a parting prophecy instead. If Catherine is to secure a position as Regent, she will need Mary's help.