CW’s “Supergirl” returns for its sixth and final season Tuesday at 9 p.m., in an episode that barely gives viewers a chance to breathe.

As “Rebirth” opens, Brainy (Jesse Rath) is dying, a victim of radiation poisoning. To save him, Supergirl (Melissa Benoist) and her pals must face off against a power-mad Gamenmae (Cara Buono).

That battle all takes place before the opening credit tag.

“Supergirl” has places to go and millions to save, so there’s no time to waste.

With Mommy Luthor’s (Brenda Strong) help, Lex (Jon Cryer) has transformed himself into something akin to a mythic god from Olympus.

A word about Cryer, who looks as if he’s having the best time of his career: His Luthor is sadistic, vile, and absolutely hilarious. You don’t want to like the guy, but he’s utterly magnetic.

Making himself invincible is just one part of his plan. The other hinges on using a dozen satellites orbiting the planet to destroy half the population – that’s his idea of “saving” humanity.

And then it’s on to remaking every other planet in the universe to his liking.

Lex Luthor is nothing but a man with a few ambitions.

Supergirl realizes there’s only one way to stop Lex: She has to make the ultimate sacrifice. She has to surrender to Luthor.

Supergirl’s friends are aghast at the thought. Lena (Katie McGrath) is especially remorseful for her previous actions and wishes to prove herself.

But time runs short, and a deadly encounter at the Fortress of Solitude will change everyone.

In its final season, “Supergirl” looks to up the ante on its storytelling.

This viewer can only hope the show will get around to revisiting some old, missed friends – such as Calista Flockhart’s delightful Cat Grant and Chris Wood’s Mon-El (Benoist’s real-life husband and Supergirl’s most heartfelt romantic connection).

Is it too much to wish for another musical crossover with “The Flash’s” Grant Gustin? Probably.

“Supergirl” is soaring this season, and it doesn’t look as if it has any time for song and dance.