Supergirl season 3
Kara and Mon El in Supergirl season 2 The CW

Supergirl season 3 returns this Monday (9 October) at 8pm EST on The CW Network, where Kara Danvers will cope with the loss of her boyfriend, Mon-El, by burying herself in work and saving National City against a mysterious new threat.

Episode 1 is titled, Girl of Steel, and the official synopsis reads as follows:

Kara (Melissa Benoist) deals with the loss of Mon-El (Chris Wood) by focusing all her energy on being Supergirl and the mysterious new threat against National City. Alex (Chyler Leigh) confesses a secret to Maggie (guest star Floriana Lima) about their impending nuptials. A citizen of National City has a mysterious connection to Kara, and Lena (Katie McGrath) makes a bold move.

Click here to watch The Flash season 3 episode 3 live via The CW app. You can also watch the episode online by clicking here (only in the US).

Following the tragic events of season 2 finale, Kara will take a dark turn by pushing aside her humanity, according to actress Melissa Benoist. She told Entertainment Weekly, "She's really fragile at the top of the season, but only people closest to her will see that, because she's almost solidified on the exterior and is really trying to push down whatever pain she's felt about losing Mon-El."

"In turn, she has made this massive decision to say goodbye to her humanity and really embrace being an alien. We hear her say quite a bit in the first five episodes, 'I'm not a human, I come from a different planet, so this doesn't apply to me,'" the Supergirl actress said of her character in season 3.

Naturally, the loss of the bubbly and optimistic side of Kara Danvers will not sit well with her close friend and families.

Actress Chyler Leigh who plays Kara's sister Alex told EW, "All of the friends, Alex included, are trying to help her through it, but she's just shutting a lot of people out, as a lot of us do in real life."

"Alex does everything that she can to give space, but it comes to a head pretty quickly just because Alex is obviously very honest, and the two of them have such a great and supportive relationship," she concluded.