Mary learns there's a traitor within her inner circle of advisers, and she's determined to unmask the guilty party. Meanwhile, Elizabeth seeks Narcisse's help as she tries to expand her power; and Catherine is desperate to reclaim some of her lost power.

Cast: Adelaide Kane, Megan Follows, Rachel Skarsten, Craig Parker, Rose Williams, Charlie Carrick, Ben Geurens, Tanya Bevan, Sara Garcia, Jonathan Goad, Eric Hicks, Claire Hunter, Dan Jeannotte, Will Kemp, Adam Maros