Season 2

Episode Title: The Adventures of Supergirl (Season 2, Episode 1)
Original Airdate: October 10, 2016
Supergirl and Clark team up to stop a new threat emerging in National City; Alex feels left out while Kara's family stays in town; a pod comes crashing down to earth.

Episode Title: The Last Children of Krypton (Season 2, Episode 2)
Original Airdate: October 17, 2016
Supergirl is seriously hurt when a kryptonite-powered villain attacks National City; Superman blames Hank for the attack after discovering the kryptonite was stolen from the DEO; Kara meets her boss, Snapper Carr, on her first day at her new job.

Episode Title: Welcome To Earth (Season 2, Episode 3)
Original Airdate: October 24, 2016
Alex and Detective Sawyer investigate an attack on the president; Kara searches for a recently escaped alien she thinks is behind the assault.

Episode Title: Survivors (Season 2, Episode 4)
Original Airdate: October 31, 2016
While investigating the murder of an unregistered alien, Kara and Alex find an alien fight club run by Roulette; Hank tries to get to know M'Gann better; Supergirl begins to train Mon-El.

Episode Title: Crossfire (Season 2, Episode 5)
Original Airdate: November 7, 2016
Supergirl battles a ruthless new gang with dangerous alien technology; the team discovers Cadmus is staffing the criminals for a secret mission; Mon-El gets a job as an intern at CatCo; Lena invites Kara to a fundraiser.

Episode Title: Changing (Season 2, Episode 6)
Original Airdate: November 14, 2016
The Guardian comes to help after a parasite alien drains Supergirl's powers; Mon-El considers a new career; Alex copes with a new reality.

Episode Title: The Darkest Place (Season 2, Episode 7)
Original Airdate: November 21, 2016
Guardian tries to clear his name after he's accused of a murder committed by another vigilante; while on a mission to rescue Mon-El, who was captured by CADMUS, Supergirl comes face to face with Cyborg Superman.

Episode Title: Medusa (Season 2, Episode 8)
Original Airdate: November 28, 2016
When Eliza visits for Thanksgiving, Alex decides to come out to her; Winn and James consider revealing the truth about the Guardian to Kara; Barry Allen and Cisco Ramon seek Kara's help with an alien invasion.

Episode Title: Supergirl Lives (Season 2, Episode 9)
Original Airdate: January 23, 2017
When Kara investigates the story of a missing woman, she and Mon-El end up being thrust through a portal to another planet where the downtrodden are sold as slaves.

Episode Title: We Can Be Heroes (Season 2, Episode 10)
Original Airdate: January 30, 2017
Livewire seemingly breaks out of prison; Supergirl takes Mon-El with her when she sees Livewire attack the NCPD; James wants to come clean with Kara; M'Gann has a psychic attack.

Episode Title: The Martian Chronicles (Season 2, Episode 11)
Original Airdate: February 6, 2017
Armek, a white Martian, descends on National City intent on taking M'gann back to Mars to face her punishment as a traitor.

Episode Title: Luthors (Season 2, Episode 12)
Original Airdate: February 13, 2017
After Metallo breaks out of prison and frees Lillian Luthor, Lena is arrested by the police and blamed for the escape; Alex introduces Maggie to the gang.

Episode Title: Mr. & Mrs. Mxyzptlk (Season 2, Episode 13)
Original Airdate: February 20, 2017
A magical imp shows up on Earth, and after declaring his love for Kara, begins to wreak havoc on National City; Alex and Maggie celebrate their first Valentine's Day together.

Episode Title: Homecoming (Season 2, Episode 14)
Original Airdate: February 27, 2017
Alex and Kara are thrilled when Jeremiah Danvers is rescued from Cadmus, but things go awry when a suspicious Mon-El questions Jeremiah about his sudden return.

Episode Title: Exodus (Season 2, Episode 15)
Original Airdate: March 6, 2017
Alex searches for Jeremiah while Kara investigates a series of alien abductions; in an effort to get Snapper Carr to run a story that would help her stop Cadmus, Kara agrees to set up an interview between Snapper and Supergirl.

Episode Title: Star-Crossed (Season 2, Episode 16)
Original Airdate: March 20, 2017
A new villain in National City puts Supergirl on high alert; Winn's girlfriend gets him in trouble with the law; Maggie tries unsuccessfully to help Winn; the Music Meister attacks Supergirl.
***"Part 2" of this episode continued the next night (March 21, 2017) on The Flash (episode description below)
The Flash Episode Title: Duet (Season 3, Episode 17)
Mon-El and Hank Henshaw arrive carrying a comatose Supergirl, who was attacked by the Music Meister; when the Music Meister attacks Barry, both he and Supergirl wake up in an alternate reality that they have to sing and dance their way out of.***

Episode Title: Distant Sun (Season 2, Episode 17)
Original Airdate: March 27, 2017
A large bounty on Supergirl draws aliens from all over to National City; Alex and Maggie run into Maggie's ex-girlfriend; Hank receives an interesting order from the president.

Episode Title: Ace Reporter (Season 2, Episode 18)
Original Airdate: April 24, 2017
Lena's ex-boyfriend comes to National City to unveil his nano-technology breakthrough; Lena asks Kara to attend Jack's conference with her for support.

Episode Title: Alex (Season 2, Episode 19)
Original Airdate: May 1, 2017
Alex gets kidnapped and her captor threatens to kill her unless Supergirl releases a notorious criminal from prison; Rhea has an interesting proposal for Lena.

Episode Title: City of Lost Children (Season 2, Episode 20)
Original Airdate: May 8, 2017
It's up to Guardian to intervene when an alien that has telekinetic powers attacks National City; Rhea's plan escalates.

Episode Title: Resist (Season 2, Episode 21)
Original Airdate: May 15, 2017
Supergirl struggles to decide whether or not to obey the president's orders regarding Rhea's latest actions; Cat Grant returns to National City.

Episode Title: Nevertheless, She Persisted (Season 2, Episode 22)
Original Airdate: May 22, 2017
Supergirl challenges Rhea to battle to save National City; Superman returns; Cat Grant offers Supergirl some sage advice.