CBS has released the official synopsis and 2 photos for the December 7th episode of Supergirl, which will feature Charles Halford as Jemm and a powerless Kara determined to help after an earthquake.

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.

Halford most recently played Chas Chandler on NBC's short-lived comic book series Constantine.

Jemm, Son of Saturn, is a superhero in DC Comics and a Martian Manhunter ally. He possesses super-strength, flight, telepathy and psychokinetic blasts. He was created in 1984 by Greg Potter and Gene Colan. The gemstone embedded in his forehead allows him to sense the emotions of others. He can also use it to manipulate people's emotions.

The episode was directed by Larry Teng and written by Yahlin Chang and Ted Sullivan.

“Human For a Day” episode of Supergirl will air Monday, December 7 at 8PM on CBS.