Over their time together in France, for the first three seasons of “Reign,” Catherine (Megan Follows) went from trying to kill Mary (Adelaide Kane) to grooming her as somewhat of a protege. Mary’s instincts always tended towards trusting others and following her heart, but under the tutelage of her mother-in-law, she was taught to be ruthless and single-minded, protecting her country and family above all else.

Regrettably, Catherine’s family includes both a dominating Italian monarchy as well as a stable of French heirs to the throne. She’s got all the French royals in her back pocket and, other than the occasional time spent in the dungeon, has built up a network of informants that keep her out of trouble and — as we see in “Hanging Swords” (March 31) — help her track down one wayward son in record time.

RELATED: Queen Mary leans into her panic attacks in a surprising way as the doomed ‘Reign’ wedding approaches

Mary, on the flip side, is an orphan whose only family member is a half-brother still agitated to be ruled by a girl, and whose overprotectiveness continues to have a sort of Lannister sheen; it seems unlikely that any prospective suitor would pass muster with James (Dan Jeannotte). While tension is high between Catholics and Protestants across Western Europe, with Mary’s rule still tenuous, Scotland is far likelier to succumb to a religious war than France anytime soon, even given Charles’ (Spencer MacPherson) grab for attention via converting to Protestantism.

reign hanging swords megan follows anastasia phillips catherine leeza1 For Reigns Mary & Elizabeth, character is destiny    and that can be deadly

Mary needs Darnley (Will Kemp) as a husband not just to strengthen her claim on the English throne, but also so she can begin the business of birthing her own heirs — personally populating Scotland, and hopefully England, with a new Stuart dynasty. As a woman and a person, she needs companionship, loyalty, and someone she can trust; even with the baby steps she’s made with her fiance, Darnley’s propensity toward shifty-eyed looks cannot be ignored. Last week, she concluded it was her memories of Francis (Toby Regbo) that caused her to panic when she got too close to Darnley; this week, she’s still got a sense that something is going to go wrong, and if she can only nip it in the bud maybe things will turn out okay.

What we know and she doesn’t, for most of the episode, is that Darnley’s former lover Keira (Sara Garcia) has thrown herself into the powder keg of Scottish court, Glenn Close “Fatal Attraction” style, desperate for any scraps of affection Darnley has left to offer her. But we’ve seen enough of Darnley to know if it wasn’t Keira, it would have been someone or something else; that Mary knows at this early stage how fickle he can be is better than learning it ten years into a disastrous marriage.

Still, between last week’s free-floating panic and this week’s sense of impending trouble, we can’t help imagining the strength of history doubling back on itself — screaming at her subconscious to abort this engagement.

reign hanging swords spencer macpherson charles1 For Reigns Mary & Elizabeth, character is destiny    and that can be deadly

And yet, as ever, Catherine’s lessons clearly are still sticking with her. Mary is furious with Darnley for betraying her before they’ve even married — but her country’s needs, and her personal safety, demand that she carry on with this marriage. As both Mary and Elizabeth (Rachel Skarsten) brush up against this week, just because you’re a Queen doesn’t mean you can do or get whatever you want. As Catherine has always known, the person who seems to have the most power is quite often the person least able to exert their own will.

RELATED: ‘The White Princess’ exclusive: Exploring the Lancaster & York family trees

Prior to Darnley’s betrayal, Mary had lightly fantasized about eloping with him, to a picturesque meadow. She is aware, even as she voices the dream, that it could never happen — but part of her still wants it to, clinging to the romantic optimism she’s held onto since returning to French court in the “Reign” pilot.

If rival Elizabeth has ever thought anything along these lines, she’s known enough not to voice it: While both girls were raised basically as orphans, Elizabeth — as she reminds us this week — lived through her mother’s beheading and vilification, was raised as a bastard away from Court, thrown in jail by her sister and came to accept that death would be a blessing to take her away from the misery of her life.

reign hanging swords megan follows craig parker catherine narcisse1 For Reigns Mary & Elizabeth, character is destiny    and that can be deadly

While Mary was raised as a Queen in absentia, Elizabeth was dropped into a world of terror and left to fend for herself, so retaining power is a more primal need; she eschewed her only love last season and has been singleminded in her pursuit of power ever since. It’s the thing where those atop the ladder can read about what it’s like to work your way up, but they’ll never know how it feels to live without support. Those of us who work our way up remember how it felt to be living on the outside, have seen how easily it can be taken from you, and work harder to retain their power — and perhaps this is Elizabeth’s trump card: Mary may feel occasionally like she’s struggling against an undertow, but Elizabeth knows she is — and never forgets it.

RELATED: The original gig economy: ‘Harlots’ is a parable of economic compromise

“I grew up with a sword hanging over my head, aware at any moment I could be slain,” as Elizabeth describes it to Gideon (Ben Geurens), her adviser and only friend, in a moment of rare vulnerability. Of the three women at the heart of this show, Elizabeth is the only one to have truly experienced both sides of this coin: The clarity of knowing death would find her sooner rather than later despite her innocence; the way she knows into the marrow in her bones that her power can be taken away at any time. While Mary’s only course of action is to marry a man she now loathes, Elizabeth’s path runs parallel; she can rely only on herself.

It’s taken all this time for Mary to finally accept she’s playing a zero-sum game, one on which both of their parallel paths have been set and, for the time being, could wind up with either woman on the English throne. Mary’s ace is the time she spent with Catherine, who forced her to harden and make the difficult decisions, teaching her how it is to rule as a woman in this world. And perhaps that could be enough… Against a different opponent.

But Elizabeth — with no mentor we’ve ever seen, who survives and always has through sheer power of will — is unlike any opponent Catherine, or anyone, could have prepared Mary for.

“Reign” airs Fridays at 8 p.m. ET/PT on The CW.

Posted by:Ann Foster

Freelance writer on the Canadian prairies.