Kara at age 12 was sent from her dying home planet of Krypton to Earth, where she was taken in by the Danvers, a foster family who taught her to be careful with her extraordinary powers. After repressing said skills for more than a decade, Kara is forced to bust out her super moves in public during an unexpected disaster. Energized by her heroism for the first time in her life, she begins embracing her abilities in the name of helping the people of her city, earning herself a super moniker along the way.
When Kara's attempts to help National City don't go according to plan, she must put aside the doubts that she - and the city's media - has about her abilities in order to capture an escapee from the Kryptonian prison, Fort Rozz. Also, Cat pressures James to use his connection to Superman to get her an interview with Supergirl.
Supergirl's powers are tested when Reactron, one of Superman's formidable enemies, arrives in National City and targets the young hero. Also, Cat plans to run an exposé on Supergirl.
Kara's Thanksgiving may be ruined when she suspects her foster mother, Dr. Danvers, who is coming to town, disapproves of her new role as a superhero. Also, when an accident transforms a volatile CatCo employee into the villainous Livewire, she targets Cat and Supergirl.
Kara's two identities are stretched thin when Supergirl must protect National City from a series of bombings and Kara is tasked with babysitting Cat's son, Carter. Also, James is conflicted when his ex-girlfriend Lucy Lane seeks to rekindle their relationship.
Personal and professional stress get the better of Kara when she goes too far during a training exercise against Red Tornado, a military cyborg commissioned by Lucy Lane's father, General Sam Lane. Also, Cat's tough exterior is shaken by a visit from her judgmental mother, Katherine, and Alex enlists Winn to look into her father's mysterious death.
Kara and her friends must rely on their inner strength and courage when an earthquake strikes National City. Also, Alex's mistrust of Hank reaches a breaking point when the earthquake traps them in the DEO with Jemm, a powerful alien escapee.
Kara goes toe-to-toe with Astra when her aunt challenges Kara's beliefs about her mother. Also, Cat is threatened with being removed as the CEO of CatCo after a hacker exposes her private and damaging emails.
With Astra in captivity at the DEO, her husband, Non, captures Hank, leading to a tense standoff between the two sides. Also, Kara continues to refute Cat's allegations that she is Supergirl.
The villainous Toyman breaks out of prison, and Kara soon discovers that he is the father of her friend Winn. While Supergirl tries to bring the villain to justice, Alex persuade Hank to use his Martian powers to break into Lord Technologies while she distracts Max with a dinner date.
Kara must help Hank face his painful past when a White Martian, a member of the alien race that wiped out his people, kidnaps Senator Miranda Crane, an anti-alien politician. Cat's estranged son, Adam, arrives in National City.
Max unleashes his new creation, dubbed "Bizarro", to hug Supergirl. While Supergirl and the DEO try to come up with a way to stop the creature, Adam and Kara grow closer, and Winn gives James some romantic advice.
Kara's friends must find a way to save her life when a parasitic alien attaches itself to her and traps her in a dream world where her family is alive and her home planet was never destroyed. Also, Alex, Hank and the DEO must fend off a Kryptonian attack while Kara is out of commission.
Supergirl goes up against a villain calling himself Master Jailer, who is intent on capturing the Fort Rozz prisoners and executing them. Meanwhile, Kara tries to deal with a rival at work, and James finds himself caught i the middle when Lucy learns that he's been lying about his involvement with Supergirl.
A computer construct from Krypton, Indigo, strikes at National City by disrupting traffic signals and leaking information. However, the DEO suspects that Indigo is up to more. Meanwhile, Lucy still has her doubts about her relationship with James, and Kara has doubts about her relationship with Hank after he seemingly cuddled her aunt.
Kara turns on her friends and the citizens of National City after being exposed to Red Kryptonite makes her malicious and dangerous. Also, Cat appears on THE TALK to discuss Supergirl.
A captive Hank details his past to the U.S. government, who suspect both him and Alex of involvement in a conspiracy. Meanwhile, Kara reveals her secret identity to someone close to the investigation in an attempt to save her friends.
Kara gains a new ally when the lightning-fast superhero The Flash suddenly appears from an alternate universe and helps Kara battle Siobhan, aka Silver Banshee, and Livewire in exchange for her help in finding a way to return him home.
Kara must find a way to free her friends when Non and Indigo use mind control to turn National City's citizens into their own army.
Supergirl is forced to do battle with an unexpected foe and must risk everything - including her life - to prevent Non and Indigo from destroying every person on the planet.