“I gave you a very powerful weapon because I trust you won’t use it,” a grave Catherine tells Mary in this exclusive clip from Reign‘s fall finale (Thursday, 9/8c). “You’ll do what needs to be done.”

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But once you find out a) what that weapon is and b) how Francis’ mom wants her future daughter-in-law to wield it, it becomes clear that Mary’s not exactly on board with the older woman’s plan. (And, incidentally, that Mary has the best seamstress in all the land.)

Press PLAY on the clip below to watch the queens clash.

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