Season 02, Episode 06 – “Changing” The Guardian makes his debut in National City to lend a hand after a parasite alien drains Supergirl of her power; at the same time, Mon-El considers a less-than-desirable career change; and Alex struggles with a new reality.
Season 02, Episode 07 – “The Darkest Place” Guardian must clear his name after being accused of a murder committed by another vigilante; at the same time, Supergirl comes face to face with Cyborg Superman while on a solo mission to rescue Mon-El, who has been captured by Cadmus.
Season 02, Episode 08 – “Medusa” A superhero crossover event begins with Barry Allen and Cisco Ramon from “The Flash” seeking Kara’s help with an alien invasion; at the same time, Eliza comes to town to celebrate Thanksgiving with her daughters, which seems like the perfect opportunity for Alex to come out to her mother. Meanwhile, Winn and James consider telling Kara the truth about the Guardian; and Kara wants to team up with Lena Luthor to combat a deadly virus unleashed by CADMUS.
Season 02, Episode 09 – “Supergirl Lives” The story of a missing woman named Izzy moves Kara to investigate, even though Snapper Carr has told her to leave the matter alone. When Kara and Mon-El check out the last place Izzy was seen, they end up thrust through a portal to another planet, where the downtrodden are sold as slaves as part of a trafficking ring run by Roulette. Meanwhile, Alex blames herself—and her new relationship with Maggie—for her sister’s disappearance.
Season 02, Episode 11 – “The Martian Chronicles” Armek arrives in National City intent on taking M’gann back to Mars to face her punishment as a traitor. Thinking she’ll be safe at the DEO, Hank and Supergirl are in for a startling surprise when shapeshifter Armek is in the building and under disguise.
Season 02, Episode 12 – “Luthors” Lena is arrested for helping break Metallo and Lillian Luthor out of prison. While the evidence seems stacked against her, Kara refuses to believe her friend is guilty and fights to clear Lena’s name. Meanwhile, Alex and Maggie celebrate Valentine’s Day.
Season 02, Episode 13 – “Mr. & Mrs. Mxyzptlk” A magical imp named Mr. Mxyzptlk shows up on Earth and declares his love for Kara, who tries to let him down easy. However, he won’t take no for an answer and starts to wreak havoc on National City. As Mon-El and Kara argue over how to get rid of Mr. Mxyzptlk, Alex and Maggie celebrate their first Valentine’s Day together.