Well, that was a very entertaining hour of television.

If there's a downside to "Resist" -- and this writer isn't sure there is -- it's that the reemergence of Calista Flockhart's Cat Grant makes it clear that Supergirl is at its best when Cat's around, and Cat's not around much anymore. That's not to say that the series doesn't have other meaningful relationships. The relationship between Alex and Kara is perhaps the show's most important, and Kara has others in her life who offer mentorship (Snapper), chosen-family love (J'onn), friendship (Lena, Winn), and other important things. Still, there's nothing quite like a good Supergirl-Car session, and that (along with the quips and speechifying) makes her return even more welcome than one might have anticipated.

The context in which she makes that grand entrance, cozily ensconced aboard Air Force One, is one among several examples of really smart plotting in "Resist." The hour begins with Rhea's invasion in full flush, with Daxamite troops attacking civilians and invading centers of power -- including the NCPD and the DEO -- as the Queen of New Daxam spouts meaningless platitudes about the new world order. Director Millicent Shelton gives us one of the series's best fight sequences to date (complete with Maggie wielding a big ol' shotgun), which concludes when Alex races right off the DEO balcony, firing at Daxamites from mid-air, and plummets toward the ground, knowing Supergirl will catch her in time. The DEO sets up headquarters in the magical dive bar, Maggie arriving not long after the Sisters Danvers do ("I’m so glad that when things looked the worst we both thought to run straight to a bar") and they're just puzzling out what to do next when another troublesome mother arrives to complicate matters.

Related: Supergirl: Mon-El Will Likely Get a Costume – Eventually

Brenda Strong's return as Lillian Luthor is understandably overshadowed by the force that is Flockhart's Grant, but it's actually more impressive from a storytelling perspective. For awhile it seemed as though Cadmus was going to rest on the back burner until the inevitable return next season of Jeremiah Danvers, but this arrival couldn't be more appropriate. Lillian and the DEO suddenly find themselves on the same side of not one but two issues -- an invading hostile alien force, and the capture of Lena. It's a smart move, as only one of those issues might not have been enough to convince Kara (and the audience) that Lillian was sincere. Smarter still is the quick nod that passes between Winn and Kara, a throwaway moment that sets up a nice, final act reversal.

After (understandably) kicking Lillian and her cronies out of the DEO's new beer-filled headquarters, the gang gets another unexpected visitor, this time in the form of an intercepted video feed from Air Force One. President Wonder Woman attempts to tell Rhea to get off her plane, but Rhea's not having it -- and that's when the Queen of All Media intervenes. It's not one of Cat Grant's best speeches (stay tuned), but it's good for infuriating Rhea into straight-up blowing up the President. Kara swoops in to save her once-and-future mentor, but she's too late to save the President... or is she? Just like that, the earlier-teased revelation that the President is herself an alien becomes known (to Cat and the DEO, at least).

Elsewhere, Rhea blackmails her poor son and would-be surrogate daughter into marriage by threatening to kill a bunch of kids. Mon-El also lets Lena know that Daxamites can reproduce using only locks of hair, which I'm sure won't come back to haunt them anytime soon. They're furious but cornered, and so Rhea busts out her best mother of the bride drag and sets to marrying them off.

Back on earth, President Wonder Woman orders the Acting DEO Director Alex Danvers (J'onn's still in his coma) to blow up the Daxamite fleet at the earliest possible moment, hostages be damned. Both Alex and Kara are distraught, Kara especially so, and when Alex tells her sister they may have to lose Mon-El and Lena to save the world, Kara heads out for some air. What she gets is a classic Cat Grant pep talk, and gosh, it's apparent from moment one how badly the show has needed one of these moments. In a nutshell, Cat reminds Supergirl that love is a value, that it defines us, and that she really ought to get to saving the people she holds near to her heart. With that, Kara zips off to bring Lillian (and Cyborn Superman) into the fold.

The plan itself is kind of silly, as the actual plans on Supergirl often are, but the general idea is that Kara, Lillian, and R2-D2 substitute Hank Henshaw will project themselves onto the ship using a tool in Superman's Fortress of Solitude while Cat distracts Rhea with a bit of patriotic, gloriously on-the-nose inspirational trolling. Assisted only by Winn, Cat delivers a barn-burner of a speech, encouraging humans and aliens alike to resist those who want to "make the world great again" at all costs. For a moment, it looks as though the "at all costs" part of the equation will get her (and her intrepid cameraman), but just as Rhea's thugs close in, Guardian swoops in to save the day. After he's dispatched with the bad guys, Guardian turns to Cat, who greets him with a "Thanks, James," a moment thats' as funny, if not funnier, than any moment in this season or the last.

In Daxam-land, Mon-El and Lena take Cat's words to heart and start working on an escape, meeting up with Supergirl in the knick of time. Kara and Mon-El have a very sweet moment in which they communicate all their relief and love without blowing Supergirl's cover, but while they're making eyes at each other, Lillian leaves them behind to die. Bad, right? Nope -- this is where Kara and Winn's conspiratorial nod comes into play, as Winn's failsafe transports Mon-El safely down to earth. Kara stays behind because, in Doctor Who fashion, she wants to give Lillian one more chance to surrender.

As this is happening, Alex keeps delaying and delaying the detonation of the cannon that will destroy the ship (a choice that greatly aggrieves the President and which will, one would think, possibly cost Alex her job), afraid she'll have to kill her beloved sister (a fear made palpable in their tearful, and very affecting, goodbye). Just as the President seems prepared to relieve Alex of duty and make someone else push the button, Rhea plays her next card, destroying the cannon with something that looks mysteriously like a superhero's ice vision. Alex's horror at that moment is one of the episode's smaller, subtler gut punches -- if the Daxamites win, Alex seems to think, it will be her own hesitation that brought that ending about.

In the final moments, we see a bit of why an incensed Rhea seemed so full of confidence, as Superman, clearly under some form of mind control, winds up and delivers a hell of a punch, right to Kara's kisser. It'll take more than a few Cat Grant bon mots to fix this situation.

Next week: Clark and Kara face-off; Rhea still thinks she's making that tiara work.

Airing Mondays at 8 p.m. ET/PT on The CW, “Supergirl” stars Melissa Benoist, Mehcad Brooks, Chyler Leigh, Jeremy Jordan, David Harewood and Chris Wood.