Supergirl Season 4 Episode Guide and Reviews

Here's everything you need to know about Supergirl season 4.

Supergirl Season 4 is now over! We’ve got everything you need to know about Supergirl season 4, as well as a complete episode guide, all in one place.

Supergirl Season 4 Episodes

Supergirl Season 4 Episode 1: American Alien

“Diving back into reporting, Kara (Melissa Benoist) welcomes a new cub reporter to CatCo.  Meanwhile, James (Mehcad Brooks) and Lena (Katie McGrath) argue about James’ impending indictment for acting as the vigilante Guardian, while Alex (Chyler Leigh) and Brainy (Jesse Rath) struggle to get in sync at the DEO. Supergirl (Melissa Benoist) is called into action when remnants of the anti-alien terrorist organization Cadmus try to assassinate pro-alien leaders, but their endgame turns out to be much more sinister than she expected. J’onn (David Harewood) relishes his peaceful new life, but an outing with an old friend causes him concern.”

airdate: 10/14/18

read our review of “American Alien” here.

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Supergirl Season 4 Episode 2: Fallout

“A shocking revelation causes chaos in National City. Supergirl (Melissa Benoist) sets out to capture Mercy Graves (guest star Rhona Mitra), while Alex (Chyler Leigh) takes control at the DEO. Back at CatCo, Kara decides to write an investigative story on Mercy and asks Lena (Katie McGrath) if she can interview her as Mercy has ties to the Luthors. Meanwhile, Brainy (Jesse Rath) meets Nia (Nicole Maines) and the two end up in a precarious situation on Supergirl.”

airdate: 10/21/18

read our review of “Fallout” here.

Supergirl Season 4 Episode 3: Man of Steel

“Ben Lockwood (Sam Witwer) didn’t always hate aliens.  Through a series of incidents, and input from his anti-alien father (guest star Xander Berkeley), Ben slowly transforms from a mild-mannered professor into the villainous Agent Liberty of today.”

airdate: 10/28/18

Supergirl Season 4 Episode 4: Ahimsa

When Supergirl (Melissa Benoist) needs help, Alex (Chyler Leigh) asks Lena (Katie McGrath) and Brainiac (Jesse Rath) to team up.  Meanwhile, J’onn (David Haredwood) questions his decision to quit the DEO. However, after running into Manchester Black (guest star David Ajala), he realizes there are a lot of ways to help his fellow aliens during this tumultuous time.”

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airdate: 11/4/18

read our review of “Ahimsa” right here.

Supergirl Season 4 Episode 5: Parasite Lost

Colonel Haley (April Parker Jones) makes a surprising decision regarding Supergirl (Melissa Benoist). Kara writes a series of articles highlighting aliens in National City in the hopes that humans will stop being so fearful of them.  Unfortunately, the article puts some of the aliens in harm’s way.”

airdate: 11/11/18

read our review of “Parasite Lost” here.

Supergirl Season 4 Episode 6: Call to Action

Everyone gathers for Thanksgiving but Kara (Melissa Benoist) is feeling down after her televised debate with Ben Lockwood (Sam Witwer) about the anti-alien sentiment coursing through National City.  Meanwhile, James (Mehcad Brooks) and Lena (Katie McGrath) argue about the best way to handle the Children of Liberty.”

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airdate: 11/18/18

read our review of “Call to Action” here.

Supergirl Season 4 Episode 7: Rather the Fallen Angel

James (Mehcad Brooks) falls in deeper with the Children of Liberty in his efforts to meet Agent Liberty (Sam Witwer).  Meanwhile, Supergirl (Melissa Benoist) and Manchester Black (guest star David Ajala) follow a lead on Agent Liberty’s location, but things take a dark turn.”

airdate: 11/25/18

read our review of “Rather the Fallen Angel” here.

Supergirl Season 4 Episode 8: Bunker Hill

“Nia (Nicole Maines) has a powerful dream about Agent Liberty (Sam Witwer) but refuses to look at it as a prophetic dream and pushes it aside.  After noticing something is bothering Nia, Kara (Melissa Benoist) enlists Brainy’s (Jesse Rath) help, and the two try to persuade Nia to embrace her destiny.”

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airdate: 12/2/18

read our review of “Bunker Hill” here.

Supergirl Season 4 Episode 9: Elseworlds Part 3

“Supergirl (Melissa Benoist), The Flash (guest star Grant Gustin), Green Arrow (guest star Stephen Amell) and Superman (guest star Tyler Hoechlin) engage in the battle of their lives.”

airdate: 12/11/18

Read our review of “Elseworlds Part 3” right here. And you can check out all the easter eggs we found in the “Elseworlds” crossover right here.

Supergirl Season 4 Episode 10: Suspicious Minds

Colonel Haley (April Parker Jones) is upset after Supergirl (Melissa Benoist) responds to a distress call from a Navy ship that turned out to be a deadly alien attack.  Colonel Haley reclaims the site as DEO territory and demands that Supergirl step aside. After Supergirl refuses to be told what to do, Haley refocuses her energy on finding out Supergirl’s true identity and begins to interrogate all DEO agents, including Alex (Chyler Leigh).”

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airdate: 1/20/19

Supergirl Season 4 Episode 11: Blood Memory

Kara (Melissa Benoist) joins Nia (Nicole Maines) on a trip to Nia’s hometown to visit her family during the town’s annual Harvest Festival.  While home, Nia’s mother (guest star Kate Burton) encourages her daughter to embrace her destiny. Meanwhile, Alex (Chyler Leigh) deals with a street drug that is turning people violent and giving them temporary superpowers.”

air date: 1/27/19

read our review of “Blood Memory” here.

Supergirl Season 4 Episode 12: Menagerie

“With his P.I. shingle newly hung outside his office, J’onn (David Harewood) welcomes new clients.  Trying to take her mind off what happened at the DEO, Kara (Melissa Benoist) decides to team up with J’onn on his latest assignment, which unfortunately ends up tying directly into Alex’s (Chyler Leigh) current investigation that involves the villain Menagerie (guest star Jessica Meraz).  Meanwhile, Lena (Katie McGrath) shares some news with James (Mehcad Brooks), but his reaction isn’t what she expected. Nia (Nicole Maines) invites Brainy (Jesse Rath) to her Valentine’s Day party.”

air date: 2/17/19

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read our review of “Menagerie” here.

Supergirl Season 4 Episode 13: What’s So Funny About Truth, Justice, and the American Way?

Manchester Black (guest star David Ajala) breaks out of prison with the help of his new team, The Elite, who are set on punishing the anti-alien forces.  Supergirl (Melissa Benoist) pulls double duty as she tries to apprehend Manchester Black and his team as well as deal with a shocking new development with Ben Lockwood (Sam Witwer).”

air date: 3/3/19

read our review of “What’s So Funny About Truth, Justice, and the American Way” right here.

Supergirl Season 4 Episode 14: Stand and Deliver

Between Ben Lockwood’s (Sam Witwer) new push to stir up the anti-alien movement and the Elite’s desire to target Lockwood and his minions, Supergirl (Melissa Benoist) is concerned about the safety of the American people – both human and alien. When Lockwood organizes a rally, the aliens decide to peacefully protest. Brainiac (Jesse Rath) and J’onn (David Harewood) join the alien march while Supergirl and Dreamer (Nicole Maines) patrol to keep everyone safe. Meanwhile, James (Mehcad Brooks) picks up his camera again to cover the march for CatCo, and Hayley (April Parker Jones) assigns Alex (Chyler Leigh) a job that clashes with her beliefs.  When The Elite and Ben Lockwood stir up trouble at the rally, Supergirl is forced to take a stand.”

air date: 3/10/19

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Supergirl Season 4 Episode 15: O, Brother, Where Art Thou?

“Secretly furloughed from prison due to failing health, Lex Luthor (guest star Jon Cryer) visits his sister, Lena (Katie McGrath), to seek her help finding a cure. Savvy as ever, Lena is suspicious of Lex’s motives but when she’s faced with a life and death situation, she must decide how she truly feels about her brother. Meanwhile, Supergirl (Melissa Benoist) and J’onn (David Harewood) face off against Manchester Black (guest star David Ajala).  James’ sister Kelly (guest star Azie Tesfai) comes to town.”

air date: 3/17/19

read our review of “O, Brother, Where Art Thou?” here!

Supergirl Season 4 Episode 16: The House of L

In the wake of Lex Luthor’s (guest star Jon Cryer) return, the show flashes back to what he’s been doing for the last two years and how his secret machinations and plans have affected Supergirl (Melissa Benoist) and Lena (Katie McGrath).”

air date: 3/24/19

read our review of “The House of L” here.

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Supergirl Season 4 Episode 17: All About Eve

“Supergirl (Melissa Benoist) must deal with the destructive aftermath of Lex’s (guest star Jon Cryer) nefarious plans. Shocked at what Lex has created, Supergirl faces her biggest challenge yet.”

air date: 3/31/19

read our review of “All About Eve” here.

Supergirl Season 4 Episode 18: Crime and Punishment

Kara (Melissa Benoist) and Lena (Katie McGrath) head to Stryker’s Island to search for clues on how to defeat Lex.  At the prison, Kara tries to befriend a nosy prisoner, Steve (guest star Willie Garson), who may have insight into what Lex was doing, while Lena studies an array of puzzles Lex left behind in the hopes of discovering his whereabouts.  While there, a prison riot breaks out and Kara must find a way to stop the prisoners without revealing her secret identity as Supergirl. Meanwhile, Kelly (guest star Azie Tesfai) encourages James (Mehcad Brooks) to talk to someone for his PTSD, and Alex (Chyler Leigh) faces off against Ben Lockwood (Sam Witwer) after he storms the DEO and acquires some powerful weapons to hunt Supergirl.”

air date: 4/21/19

Supergirl Season 4 Episode 19: American Dreamer

As Kara (Melissa Benoist) doggedly works as a reporter to clear Supergirl’s name, Dreamer (Nicole Maines) picks up the slack as National City’s protector, which leads to a showdown with Ben Lockwood (Sam Witwer).  James (Mehcad Brooks) takes drastic measures to relieve his PTSD.”

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air date: 4/28/19

You can read our review of “American Dreamer” right here.

Supergirl Season 4 Episode 20: Will the Real Miss Tessmacher Please Stand Up?

Kara (Melissa Benoist) and Lena (Katie McGrath) head to Kaznia to hunt down Lex. However, Eve Tessmacher (guest star Andrea Brooks) sets a trap for the duo that could ultimately reveal that Kara is Supergirl.  Meanwhile, Alex (Chyler Leigh) gets a long-awaited phone call, James (Mehcad Brooks) practices using his powers, and Ben Lockwood (Sam Witwer) takes a dangerous stand inside the DEO.”

air date: 5/5/19

read our review of “Will the Real Miss Tessmacher Please Stand Up” right here.

Supergirl Season 4 Episode 21: Red Dawn

Kara (Melissa Benoist) comes face to face with Red Daughter and the two engage in an epic battle. Determined to find a way to extract the Harun-El, Lena (Katie McGrath) turns to an unlikely source for help – Lillian Luthor (guest star Brenda Strong). Meanwhile, Alex (Chyler Leigh) realizes she’s missing parts of her memory, and Brainy (Jesse Rath), Nia (Nicole Maines) and J’onn (David Harewood) set out to track down aliens who have been abducted by Lex.”

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air date: 5/12/19

You can read our review of “Red Dawn” right here.

Supergirl Season 4 Episode 22: The Quest for Peace

Lex Luthor (guest star Jon Cryer) descends upon Washington, DC and summons Lena (Katie McGrath) and Lillian Luthor (guest star Brenda Strong) to the White House.  Supergirl (Melissa Benoist) realizes she has one last chance to stop Lex and turns to the power of the press to help her.”

air date: 5/19/19

read our review of “The Quest for Peace” here.

Supergirl Season 4 Cast

Konechny is Agent Jensen, described by Deadline as “a DEO agent recruited by Alex (Chyler Leigh) who struggles to find his footing at the DEO.”

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Tyler Hoechlin returns as Superman as part of this year’s Arrowverse crossover, but the show will also introduce Lois Lane! We have more details on that here.

Brent Spiner had been announced as Vice President Baker, but he was replaced by Bruce Boxleitner. We have more details on his character here.

Nicole Maines is Nia Nal, “the newest addition to the CatCo reporting team. A soulful young transgender woman with a fierce drive to protect others, Nia’s journey this season means fulfilling her destiny as the superhero Dreamer (much like Kara came into her own as Supergirl).” We have more details on her character right here and our first look at Nicole Maines as Dreamer! 

April Parker Jones is Colonel Haley, a “hardline career military woman [who] lives and dies by the orders of her commanding officers. Dedicated to her country, she always acts in its best interest — even if it’s not her own.”

David Ajala is Manchester Black, “the type of guy who brings a knife to a gunfight and still walks away the winner. With a dark past, he easily deflects the brutality of his mission with his charm and sense of humor.” We have more details on his character right here.

Rhona Mitra is Mercy Graves, “an ex-CADMUS agent who  has always believed in human exceptionalism. But with both Lex and Lillian in prison, Mercy is stepping out of the Luthor shadow and running her own show. With her biting wit and lethal brawn, Mercy steadily becomes a key figure in National City’s growing ‘human-first’ movement.”

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Robert Baker is Otis Graves, “Mercy’s defacto right hand man. What he lacks in brains, he makes up for with his savant-like abilities to assassinate aliens.” (both of those character descriptions come via Deadline).

Perhaps the biggest news of the season is that Jon Cryer is playing Lex Luthor. We have more details on his casting and the show’s take on Lex right here.

Jeremy Jordan will no longer be a series regular, instead he’ll be a recurring character. This news comes via TV Line. Jesse Rath’s Brainiac 5 will be a series regular, instead.

TV Line also reports that Chris Wood won’t be back as Mon-El, as the plan was always for the character to have a two season arc. Now that’s completed, so…adios!

Supergirl Season 4 Villain

Sam Witwer will play Agent Liberty. That’s his voice you heard in the trailer, stoking xenophobia and paranoia in the name of patriotism as villains usually do. According to Entertainment Weekly

“Agent Liberty is the ruthless and terrifying founder and figurehead of Children of Liberty, a hate group that supports a human-first world order. According to a description from the show’s producers, he’s “a brilliant orator in the guise of a family man” and the scariest thing about him is how easily he can convince people that he’s right. Given that Supergirl (Melissa Benoist) and the DEO tend to be pro-alien integration, it’s definitely fair to assume they won’t get along with Agent Liberty and his Children of Liberty.”

Supergirl Season 4 Story

Here’s the official synopsis for Supergirl Season 4!

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Season three saw Supergirl stop Reign and the other Worldkillers’ threat to humanity and our planet, and in the process, Kara was shocked to find her mother Alura alive and living in a salvaged Argo City that survived the destruction of Krypton. Reconnecting with her past caused Kara to realize that her true home is now here on Earth, where big changes are taking place for her and all of her friends in National City – and also, it appears, for a doppelganger in Russia! Season four promises to be full of surprises, action, adventure and lots of big revelations for Supergirl, Alex, James, J’onn, Lena and Brainy.

We’ll update this with more information as it becomes available.

Mike Cecchini is the Editor in Chief of Den of Geek. You can read more of his work here. Follow him on Twitter @wayoutstuff.

Joseph Baxter is a contributor for Den of Geek and Syfy Wire. You can find his work here. Follow him on Twitter @josbaxter.