Supergirl - Season 4 - Eps 18: Crime and Punishment
Kara and Lena 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, 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 encourages James to talk to someone for his PTSD, and Alex faces off against Ben Lockwood after he storms the DEO and acquires some powerful weapons to hunt Supergirl.
About Supergirl

Title: Supergirl
First Air Date: 2015-10-26
Last Air Date: 2021-11-09
Status: Ended
Rating: 7.306/10 (from 4223 votes)
Language: EN
Seasons: 6
Total Episodes: 126
Network: CBS The CW
Genres: Drama, Sci-Fi & Fantasy, Action & Adventure
Production Companies: DC Entertainment, Berlanti Productions, Warner Bros. Television
Synopsis
Twenty-four-year-old Kara Zor-El, who was taken in by the Danvers family when she was 13 after being sent away from Krypton, must learn to embrace her powers after previously hiding them. The Danvers teach her to be careful with her powers, until she has to reveal them during an unexpected disaster, setting her on her journey of heroism.
Cast

Melissa Benoist
Kara Danvers / Supergirl / Kara Zor-El

Chyler Leigh
Alex Danvers / Sentinel

David Harewood
J'onn J'onzz / Martian Manhunter

Katie McGrath
Lena Luthor

Jesse Rath
Querl 'Brainy' Dox / Brainiac-5

Nicole Maines
Nia Nal / Dreamer

Azie Tesfai
Kelly Olsen / Guardian

Julie Gonzalo
Andrea Rojas / Acrata

Staz Nair
William Dey

Peta Sergeant
Nyxlygsptlnz / 'Nyxly'