“When Kara (Melissa Benoist) and Alex (Chyler Leigh) investigate the murder of an unregistered alien, the trail leads to an alien fight club run by Roulette (guest star Dichen Lachman), the ringmaster who commands aliens to fight in mortal combat for the entertainment of rich humans. While trying to stop the fighting, Supergirl and Martian Manhunter find themselves up against a surprising opponent. Meanwhile, Hank (David Harewood) is thrilled to have found another Martian and tries to get to know M’Gann (guest star Sharon Leal) better. Supergirl takes Mon-El (Chris Wood) under her wing and begins to train him.”
James Marshall directed the episode, written by Paula Yoo & Eric Carrasco.
Supergirl stars Melissa Benoist alongside Mehcad Brooks as James Olsen, Laura Benanti as Alura Zor-El, Calista Flockhart as Cat Grant, Chyler Leigh as Alexandra “Alex” Danvers, Jeremy Jordan as Winslow “Winn” Schott, Jenna Dewan Tatum as Lucy Lane (sister of Lois), David Harewood as Hank Henshaw, Peter Facinelli as Maxwell Lord, with Dean Cain and Helen Slater. Supergirl season two also features recurring roles for Katie McGrath as Lena Luthor, Floriana Lima as Maggie Sawyer, and Lynda Carter as the President of the United States.