Alex Danvers

Alexandra "Alex" Danvers Ph.D. M.D., also known as Sentinel, is a fictional character from the Arrowverse television series Supergirl, portrayed by actress Chyler Leigh. Created by executive producers Greg Berlanti, Ali Adler, and Andrew Kreisberg, the character was introduced in the pilot episode as the elder adoptive sister of protagonist Kara Danvers / Supergirl. Alex is a bioengineer, physician, scientist and a field agent of the DEO, a secret government agency that works to protect the Earth from extraterrestrial threats. She later becomes the director of the organization at the end of season three, after having been J'onn's second-in-command for years, and remains so through season five. Alex is also featured in the show's digital tie-in comic book series, Adventures of Supergirl, as well as the 2017 four-part Arrowverse crossover event "Crisis on Earth-X", with Leigh reprising her role across The Flash, Arrow, and Legends of Tomorrow. Background Alex Danvers is the only biological child of scientists Eliza and Jeremiah Danvers. When Alex was a teenager, her parents adopted an orphaned Kara Zor-El and they grew up together in the town of Midvale. Although Alex was an exceptional student, particularly in science, she couldn't help but envy her Kryptonian sister's alien abilities. Alex was relieved when Kara decided not to use her powers, but still felt embarrassed by her alien behavior. Nonetheless, as the older sister figure, Alex felt protective of Kara and sympathy for her losses and displacement. At some point, Kara took a reluctant Alex flying through the night and they were spotted by the Department of Extranormal Operations (DEO), a secret government agency tasked with monitoring alien presence on Earth. Unbeknownst to the young girls, Jeremiah agreed to work for the organization under Hank Henshaw instead of letting them take Kara away. In high school Alex had a best friend, Vicky Donahue. She enjoyed sleepovers with Vicky and developed feelings for her. Alex recognized her feelings; however, she got scared and was suddenly fighting with Vicky. This falling out was the reason why they never talked again.