In A Grain of Deception a spy threatens Mary’s trust within her inner circle.
Queen Mary (Adelaide Kane) discovers there is a leak amongst her advisors and sets out to uncover the traitor. Queen Elizabeth (Rachel Skarsten) enlists in Narcisse (Craig Parker) to further her quest for supremacy.
Meanwhile, Catherine (Megan Follows) takes desperate measures to regain some of the power she has lost.
Spencer MacPherson, Will Kemp, Dan Jeannotte, Jonathan Goad, Ben Geurens, Celina Sinden and Rose Williams also star.
Fred Gerber directed the episode, written by Patti Carr and Lara Olsen
Series: Reign Season 4 Episode 2
Airdate: 17 February 2017 on CW.