One of the most important things you learn in superhero school is that a superhero must have a secret identity for when they're off duty. It's mostly so superheroes can run errands without someone judging them for only buying a six-pack of beer and a can of vegetarian refried beans at the grocery store. Or so they can do really important things without being recognized, like, say, stalk Tom Hardy.

But many comic book series feel compelled to hide their characters' alter egos for years in order to maximize dramatic tension. And for many shows that particular storytelling device usually ends up going on for so long that it causes nothing but frustration for fans. Thankfully, Supergirl made the decision early on to bring most of its main cast into the circle of trust regarding Supergirl's secret identity as Kara Danvers (Melissa Benoist), and it's worked out quite well. Which is why it's hard to fault the writers for already bringing Maggie (Floriana Lima) into the fold too.

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In "Supergirl Lives," the first episode since The CW's four-show crossover event at the end of November, Alex (Chyler Leigh) was rightfully stressed about Supergirl having gone missing on another planet — one without a yellow sun, which meant she was essentially a normal human, just like the one she pretended to be every day at Catco. When Maggie unexpectedly arrived at the DEO, Alex told her she couldn't handle their new relationship and worry about Supergirl at the same time. Because Maggie is a detective and it is literally her job to pick up on clues — and because the two were making googley eyes at one another just that morning — she deduced that Supergirl must be Kara because Alex only ever gets that worried about her sister.

Also, the glasses are hardly a disguise.

Sure, it was kind of a cop out for Maggie to have found this out on her own offscreen, but by handling it this way, the larger ongoing plots aren't getting bogged down and we hopefully won't have to sit through any fights that arise because Alex is lying to Maggie about the identity of the hero of National City. I think we can all agree that's a good thing.

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But Alex and Maggie fans weren't the only relationship under the magnifying glass this week. Elsewhere in "Supergirl Lives," Kara and Mon-El (Chris Wood) 'shippers also had their own moment in the (yellow) sun when the latter admitted he wanted to be a superhero like Kara after witnessing her stand up and fight — without her powers — to protect the humans Roulette (Dichen Lachman in a barely-there guest appearance) was attempting to sell as slaves to an alien race on Slaver's Moon. Of course, the fact that Mon-El's career options on Earth weren't looking so good before the interplanetary travel — turns out he might like to drink but he's not a great bartender — probably had nothing to do with his new career track either.

Still, his decision probably couldn't have come at a better time. What did those aliens mean when they said Mon-El was not to be harmed? Who is he to them? What do they want? Also, if we're looking at more travel between different planets, does this mean we're getting more Stargate and Star Trek references from Winn (Jeremy Jordan)? Because we probably should.

Supergirl airs Mondays at 8/7c on The CW.