The film follows Kara Zor-El / Supergirl as she trains alongside the members of the Legion of Super-Heroes from the 31st century, and battles the terrorist organization known as the Dark Circle.

The disaster strikes early, and Alura sends her daughter Kara to Earth, where she is supposed to reunite with her younger cousin Kal-El, who is to arrive in his own escape ship.

Just after take-off, a fragment of the exploding planet damages Kara's pod, putting her into suspended animation and sending the vessel into a trajectory that arrives on Earth later than intended.

After her arrival, Kara - now named Supergirl - has trouble adjusting to life on Earth with its more primitive culture, and the superpowers gained from her new environment.

During a fight with Solomon Grundy, she spots masked individuals lurking nearby and is rescued by Kal-El (now called Superman) and Batman.

One night, while looking for school pet Proty, Triplicate Girl spots Mon-El lurking near a forbidden high-security vault on the Academy's grounds, before being attacked and apparently killed.

[b] The idea of a Legion of Super-Heroes film was conceived by Butch Lukic and Jim Krieg, who wanted to incorporate both Supergirl and the team into the Tomorrowverse.

[5] The film was confirmed by Warner Bros. Home Entertainment the next month at San Diego Comic-Con after the premiere of Green Lantern: Beware My Power.

Darren Criss, Matt Bomer, and Jensen Ackles also reprised their roles from previous DC films as Superman, Flash, and Batman, respectively.

[11] Sam Stone of Comic Book Resources wrote: "Though the movie could up the ante on some of its major set pieces, it does get to the heart of what makes the Legion tick".