After going up against non-alien bad guys like Reactron and Livewire in recent episodes, Supergirl will soon turn her attention back to extraterrestrial threats and alien escapees. As revealed by CBS, the December 7 episode of "Supergirl" will find Kara Zor-El back in DEO territory

As revealed in the synopsis, an earthquake will hit National City, keeping Supergirl and her allies busy while Supergirl's sister Alex Danvers and the less-than-trustworthy Hank Henshaw get trapped in the DEO facility with an alien escapee. The escapee in question is Jemm, the Son of Saturn, as played by Charles Halford ("Constantine").

The comic book version of Jemm debuted back in 1984's "Jemm, Son of Saturn" #1 and possesses super strength, flight, telepathy and the ability to shoot psychokinetic blasts from the gem on his forehead. Saturnians are also similar to Martians in the comics, with Jemm often teaming up with and being compared to Martian Manhunter.

The "Human For a Day" episode of "Supergirl" airs on CBS on Monday, December 7. The full synopsis for the episode is below.

"Human For a Day" - Kara and her friends must rely on their inner strength and courage when an earthquake strikes National City. Also, Alex's mistrust of Hank reaches a breaking point when the earthquake traps them in the DEO with Jemm (Charles Halford), a powerful alien escapee, on SUPERGIRL, Monday, Dec. 7 (8:00-9:00 PM, ET/PT) on the CBS Television Network.

REGULAR CAST:

Melissa Benoist (Kara Danvers/Supergirl)

Calista Flockhart (Cat Grant)

Chyler Leigh (Alex Danvers)

Mehcad Brooks (James Olsen)

David Harewood (Hank Henshaw)

Jeremy Jordan (Winslow "Winn" Schott)

RECURRING CAST:

Laura Benanti (Alura/Astra)

Peter Facinelli (Maxwell Lord)

Luke Macfarlane (Agent Donovan)

GUEST CAST:

Charles Halford (Jemm)

Ashton Bingham (Senior Tech)

David Lim (Agent Tsung)

Ayo Sorrells (Agent Reynolds)

Stephanie Arcila (Woman)

Zhuair Haddad (Store Owner)

Casey Strand (Reporter)

Bryan Lugo (Looter)

WRITTEN BY: Yahlin Chang and Ted Sullivan

BASED ON: The Characters Appearing in the DC Comics

DIRECTED BY: Larry Teng

GENRE: DRAMA