Warning: spoilers ahead for the midseason premiere of Supergirl.
Supergirl has finally returned to the airwaves after nearly two months of hiatus with an episode that shed a little more light on the big secret that Mon-El has been keeping from Kara and Co. all season. "Supergirl Lives" took Kara and Mon-El through a portal to a distant moon under a red sun, where they discovered a slave ring run by none other than Roulette. Mon-El was very nearly gunned down by an angry alien...until a Dominator stopped the attack and bowed to Mon-El in an unexpected show of respect. The final scene featured a pair of mysterious (and murderous) hooded aliens arriving on the moon in search of Mon-El.
Mon-El has been keeping a secret for a while, but "Supergirl Lives" proves that the secret is far deadlier than many of us might have guessed. The hooded aliens who are hunting him have already revealed that a little murder and mayhem is nothing if it gets them what they want, and they clearly want to get their hands on Mon-El. Now that Mon-El has been definitively connected to Supergirl on both Slaver's Moon and in National City, she could be in for a lot of trouble sooner rather than later. After all, Kara is an incredibly visible superhero. She'll fight crime and make headlines before she'll skulk in any shadows and hide her face. If the antagonistic aliens arrive on Earth and can't find the Daxamite with the lower profile, they might turn their attention on the perky Kryptonian in the bright red cape.
Of course, Kara can survive just about anything as long as she's on a planet under a yellow sun. The same can't be said for most of the people she loves in her life. Despite their remarkable abilities, Alex, Winn, and James are all human with very human vulnerabilities. J'onn has his own set of weaknesses, including simple fire. Kara can't be everywhere at once, and Mon-El may not be much help if everything starts falling apart when the evil aliens arrive on Earth. Sure, he ended "Supergirl Lives" by declaring that he wants to be a superhero with a suit and a cape and the works, but he has already proved an inconsistent ally when he faces danger. A group of aliens that has been hunting him throughout the galaxy might have the right kind of menace to scare the good intentions right out of him. If Mon-El doesn't come clean to Kara about his secret and enlist her help in figuring out why strange aliens are interested in him, disaster of pretty epic proportions could come to National City.
The big question now is what Mon-El has done - or who he is - that he is so important to random aliens throughout the galaxy. It seems that the hooded aliens are out to harm Mon-El, but the Earth-38 Dominator showed clear signs of respect to Mon-El. It seems that there is more to his backstory than he let on. Mon-El has claimed that he was a guard to a Daxamite prince, and he only survived the destruction of Daxam because the prince sent him to safety on a Kryptonian pod. Going by Mon-El's apparent infamy throughout the universe, we may now need to wonder if maybe the Daxamite prince didn't perish on Daxam. Mon-El himself could be Daxamite royalty.
Admittedly, his flashback from earlier in Season 2 definitely showed Mon-El trying to usher an injured prince to the Kryptonian pod, but the flashback doesn't explicitly say that Mon-El is a simple guard trying to protect a person in his charge. A lot of Mon-El's characterization would actually make more sense if he comes from a royal background of pampering and privilege. Many of his stories from his time on Daxam seem to revolve around activities like drinking and partying and all the kinds of shenanigans that a guardsman to a prince might not have time for on a regular basis. He also hasn't shown much natural training when it comes to combat. If Mon-El truly is a surviving Daxamite prince with aliens from all corners of the galaxy looking for him, he's bound to bring a lot of attention to wherever he goes, and the deceased scientist on Slaver's Moon could attest to the fact that attention on Mon-El can get deadly very quickly.
Hopefully we won't have to wait too long to find out more about Mon-El's big secret. For Kara's sake, Mon-El needs to 'fess up sooner rather than later to limit collateral damage when the confrontation with the hooded aliens inevitably occurs. Tune in to The CW on Mondays at 8 p.m. ET to catch new episodes of Supergirl, and don't forget to check out our midseason TV premiere schedule.