Supergirl: Was That The Legion of Super-Heroes?

Tonight's Supergirl had a pretty big callback to the show's pilot, but that wasn't the only beginning referenced in 'The Faithful'. Tonight's episode also had a call back to the mysterious ship in the season three premiere.

Spoilers for tonight's episode of Supergirl, 'The Faithful', below.

After Thomas Coville (Chad Lowe) lead his Children of Rao cult into taking the Betahedron to a packed National City arena where he intended to explode it, forcing Supergirl (Melissa Benoist) to save everyone so they could recruit them, Kara is too weak from Kryptonite exposure to fly it away. She must use her heat vision to create a hole in ground that Alex, with the help of a reluctant Coville, then pushes the Betahedron into. The Betahedron explodes, but at depth so no one is harmed.

However, at the very end of the episode it's revealed that the Betahedron's explosion did have some impact and the mysterious ship at the bottom of the harbor from the season three premiere is shown lighting up. This time, however, it's not just the outside. We go inside of the ship to find that it holds five pods -- and just before the screen goes black, a hand appears inside.

As we've speculated about who the ship belongs to before and we can now rule out at least M'rynn J'onnz, we must ask: is the Legion of Super-Heroes on this mystery ship? We already know that Saturn Girl will make an appearance this season. It was announced in September that Bollywood star Amy Jackson had been cast as Irma Ardeen -- better known as the superhero Saturn Girl -- for this season. Saturn Girl is most closely associated with the Legion of Super-Heroes.

Another clue that this mystery ship could contain the Legion of Super-Heroes is the curious symbol on the pod where the mystery person has pressed their hand. It appears to be a symbol in Interlac, a universal written language that the various aliens use to communicate in comics. The same language appears on the walls of Supergirl's alien bar and while that symbol doesn't appear on first glance to have a direct correlation to one of the known letters in Interlac, it does look a bit like their version of the number five, perhaps indicating the pod's number.

But Saturn Girl is just one of the members of the Legion. Who could be in the other pods? Presuming they also contain other members of the Legion and Saturn Girl isn't alone on the ship, Lighting Lad and Cosmic Boy -- who, in comics, are the other two heroes in the Legion's founding trio -- are likely choices. But that would leave two more pods and while the Legion has a long roster in comics since the team's debut in 1958 there is one particular hero whose arrival might make Supergirl very happy: Valor, better known as Mon-El.

In comics, Mon-El joins the Legion after Saturn Girl creates a temporary antidote to the lead poisoning that forced him off Earth and into the Phantom Zone and while it might require a little bit of explanation as to how and why Mon-El (Chris Wood) crossed paths with Saturn Girl, CW President Mark Pedowitz has hinted that Mon-El may well return this season.

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