Kara (Melissa Benoist), Hank (David Harewood), Alex (Chyler Leigh) and Maggie (Floriana Lima) find out that National City has its own underground alien fight club in Season 2, episode 4 of “Supergirl.”

According to the synopsis for the episode, entitled “Survivors,” Kara and Alex discovered the alien fight club while investigating the murder of an unregistered alien.

As seen in the trailer for the episode, Alex and Maggie go undercover to gain more information about the fight club, where aliens kill each other for the entertainment of rich humans. While masquerading as wealthy patrons of the fight club, the two appear to have seen Miss Martian (Sharon Leal) facing off against a fellow alien refugee.

After hearing the news from Alex and Maggie, Hank, also known as Martian Manhunter, pays Miss Martian a visit and pressures her to reveal the person who is running the fight club.

“She calls herself Roulette (Dichen Lachman). She has powerful friends!” Miss Martian, who also goes by name M’Gann, tells Hank in the preview clip.

Supergirl tries to shut down the fight club but finds herself inside its death-match cage with a murderous alien she needs to take down.

In the comics, Roulette, also known as Veronica Sinclair, is an enemy to the Justice Society. She runs a gambling establishment for supervillains where they can bet on different events. Instead of getting her own hands dirty, she is more of a calculating business-minded character who manipulates others for profit. Created by Geoff Johns and Rags Morales, Roulette first appeared in 2001’s “JSA Secret Files and Origins” #2.

Lachman confirmed her casting as Roulette in a clip she uploaded on Instagram last September. “I just want to thank everybody for all the excitement about me appearing on ‘Supergirl’ as Roulette,” the Nepali-born Australian actress said. “The cast and crew are working so hard and there are such incredible people. I’m really excited to be on the show, and I can’t wait for you to see it.”

Earlier today, the 34-year-old actress revealed on Instagram that she’s both “excited and nervous” about her debut episode. 

“Supergirl” Season 2, episode 4 airs on Monday, Oct. 31, at 8 p.m. on The CW.