EMMA ARRESTS MARY MARGARET FOR THE SUSPECTED MURDER OF DAVID'S WIFE, AND PRINCE CHARMING MUST STOP SNOW WHITE FROM ATTEMPTING TO ASSASSINATE THE EVIL QUEEN, ON ABC'S "ONCE UPON A TIME"

"Heart of Darkness" - Mary Margaret hires Mr. Gold as her attorney when Emma is forced to arrest her for the suspected murder of David's wife, Kathryn. Meanwhile, back in the fairytale land that was, Prince Charming sets out to stop a determined and unhinged Snow White, whose memory is still clouded by Rumplestiltskin's potion, from assassinating the Evil Queen, on "Once Upon a Time," SUNDAY, MARCH 18 (8:00-9:00 p.m., ET) on the ABC Television Network.

"Once Upon a Time" stars Ginnifer Goodwin as Snow White/Mary Margaret, Jennifer Morrison as Emma Swan, Robert Carlyle as Rumplestiltskin/Mr. Gold, Lana Parrilla as Evil Queen/Regina, Josh Dallas as Prince Charming/David, Eion Bailey as August, Jared Gilmore as Henry Mills and Raphael Sbarge as Jiminy Cricket/Archie Hopper.

Guest starring are Eion Bailey as August, Lee Arenberg as Leroy/Grumpy, Meghan Ory as Ruby/Red Riding Hood, Jim Shield as Royal Guard, Edward Foy as Black Knight, David-Paul Grove as Doc, Gabe Khouth as Mr. Clark/Sneezy, Faustino Di Bauda as Walter/Sleepy, Jeffrey Kaiser as Dopey, Michael Coleman as Happy and Mig Macario as Bashful.

"Heart of Darkness" was written by Andrew Chambliss & Ian Goldberg and directed by Dean White.

"Once Upon a Time" is broadcast in 720 Progressive (720P), ABC's selected HDTV format with a 5.1 channel surround sound. A TV parental guideline will be assigned closer to the airdate.

For more information on "Once Upon a Time," visit ABC.com/Once