The Best Episodes Written By Derek Simon

While Mike's visions and addiction to pain medications start affecting his ability to function in the field, Briggs coaxes a former FBI agent out of retirement to help take down Ari.

An attack is made on the President as hot-button, alien vs. human rights issues heat up in National City. Supergirl and the DEO are assigned to protect the President and bring in the responsible party. Alex teams up with Detective Maggie Sawyer to investigate the case while Kara searches for a recently escaped Mon-El, who she fears may be the alien behind the assault.

When Jeremiah Danvers is rescued from Cadmus, Alex and Kara are thrilled to have their father back. The Danvers arrange a family dinner to celebrate but things go awry when a suspicious Mon-El starts to question Jeremiah about his sudden return.

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 grapples with whether or not to obey the President's orders regarding Rhea's latest actions. Meanwhile, Cat Grant returns to National City.

J'onn J'onzz reveals the details of meeting Kara and Alex's father, Dr. Jeremiah Danvers, and assuming Hank Henshaw's identity. Also, Kara debates trusting someone new with her secret identity and Siobhan plots against Kara.

Struggling to heal from her injuries inflicted by Reign, Supergirl remains in a dreamlike state, unable to be reached. Mon-El recruits one of the Legion members, Brainiac-5, to try to bring her back. Meanwhile, Reign continues her rampage on the city so the DEO teams up with the Legion of Superheroes to try to stop her.

Eliza throws Alex and Maggie a wedding shower, which causes Maggie to reach out to her estranged father. Supergirl joins J’onn on a personal mission.

Ben Lockwood didn't always hate aliens. Through a series of incidents, and input from his anti-alien father, Ben slowly transforms from a mild-mannered professor into the villainous Agent Liberty of today.

Supergirl, The Flash, Green Arrow and Superman engage in the battle of their lives. The crossover starts on The Flash S05E09 Elseworlds (I) and Arrow S07E09 Elseworlds (II).

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.

When Winn’s father dies, his estranged mother, Mary, reappears trying to reconnect and to explain why she abandoned him all those years ago. Winn is too embittered from his rough childhood to forgive her but when a copycat Toyman attacks, the two must work together to stop him. Mon-El tells Kara something important about the Worldkillers, and Alex becomes suspicious of Myr'nn’s recent behavior.

Still reeling after learning about Lena’s secret, Supergirl asks Guardian for a favor that could alter his relationship with Lena forever. Meanwhile, with all three Worldkillers united, Supergirl and the team brace for an epic battle.

Eliza comes to town to celebrate Thanksgiving with her daughters. Alex decides it’s time to come out to her mother; Kara is shocked when Eliza suggests Mon-El has feelings for her, and Winn and James consider telling Kara the truth about the Guardian. Meanwhile, Cadmus unleashes a virus that instantly kills any alien in the vicinity so Kara enlists an unexpected ally – Lena Luthor. The epic superhero crossover kicks off tonight when Barry Allen and Cisco Ramon seek Kara's help with an alien invasion on their Earth. The crossover continues on The Flash S03E08 Invasion! (II), Arrow S05E08 Invasion! (III) and DC's Legends of Tomorrow S02E07 Invasion! (IV).

Supergirl realizes that in order to stop Lex and Leviathan she must work with the one person she never thought she’d trust again – Lena. Nia keeps dreaming about Brainy but struggles with what the dreams are trying to tell her. Meanwhile, Brainy realizes there is only one way to stop Lex.

Secretly furloughed from prison due to failing health, Lex Luthor visits his sister, Lena, 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 and J'onn face off against Manchester Black. James' sister Kelly comes to town.

The Monitor sends Harbinger to gather the worlds’ greatest heroes - Supergirl, The Flash, Green Arrow, Batwoman, White Canary, The Atom and Superman - in preparation for the impending Crisis. With their worlds in imminent danger, the superheroes suit up for battle while J’onn and Alex recruit Lena to help them find a way to save the people of Earth-38. This crossover continues on Batwoman S1E09, The Flash S6E09, Arrow S8E08, and Legends of Tomorrow S05E01.

Supergirl is stunned to discover that a part of Krypton survived. Meanwhile, Alex is attacked while out with Ruby, and Lena considers how far she will go to keep Reign contained.

Lex Luthor descends upon Washington, DC and summons Lena and Lillian Luthor to the White House. Supergirl realizes she has one last chance to stop Lex and turns to the power of the press to help her.

The subsequent complications from the Crisis leave Supergirl to face a chaotic threat.

Kara and Lena head to Kaznia to hunt down Lex. However, Eve Tessmacher sets a trap for the duo that could ultimately reveal that Kara is Supergirl. Meanwhile, Alex gets a long-awaited phone call, James practices using his powers, and Ben Lockwood takes a dangerous stand inside the DEO.

Mxyzptlk returns with a proposition for Kara – what if she could go back in time and tell Lena her secret before Lex did, would things turn out different? Looking back over key moments throughout the series, Kara must decide if she wants to change history to become friends with Lena again.

Kara is surprised to find that CatCo has a new owner who has brought in a star reporter. New couples emerge and explore their budding relationships while J’onn J’onzz receives an unexpected visitor.

Lena is uncertain about using her magical abilities to help Supergirl retrieve the second totem from Nyxly. William struggles to write a story on the Super Friends that makes both the heroes and Andrea happy. Meanwhile, Kelly is thrilled Esme has found a new home, but things go awry and the little girl's future is put in danger.

Supergirl and the super friends take drastic action after a loved one is kidnapped by Nyxly and Lex. An unlikely ally steps in to help the team.