Tension rises between the Catholics and the Protestants. Francis receives a gift from his dead father. Kenna is shocked by a discovery.

Bash and Francis come up with a daring plan whilst Mary has a surprising proposal for Claude.

As Mary and Francis investigate who was behind the poisoning of King Henry (Alan Van Sprang), they unearth secrets of the past which force Mary to confront her feelings for Conde as she attempts to move forward. Catherine finds herself in the middle of a romantic triangle when the Duke of Guise (guest star Gil Darnell) returns, which forces Narcisse (Craig Parker) to commit a hideous act out of desperation. Meanwhile, Greer (Celina Sinden) finds herself in a situation she never fathomed in order to survive.

Mary's mother (guest star Amy Brenneman) returns to advise Mary that her throne is in jeopardy. Mary makes a shocking proposition to Conde, along with a bold move to reclaim her throne. Francis moves closer to Lola after a setback with Mary, while King Antoine (guest star Ben Aldridge) makes Kenna an interesting offer. Megan Follows, Craig Parker, Rose Williams, Celina Sinden, Torrance Coombs and Jonathan Keltz also star.

Mary aligns herself with France as the threat of England looms; Condé makes an audacious move; Kenna and Gen. Renaude grow closer.

As Francis thinks Mary is turning against France, she risks everything to take Condé down; Catherine meets with Queen Elizabeth; Kenna's secret will seal the fate of her relationship with Bash.