DAVID AND ARTHUR EMBARK ON A HEROIC QUEST WHILE EMMA ENACTS HER PLAN TO DRAW EXCALIBUR, ON ABC'S "ONCE UPON A TIME"

Sinqua Walls Guest Stars as Lancelot, Joana Metrass Guest Stars as Guinevere and Liam Garrigan Guest Stars as King Arthur

"Siege Perilous" - In Camelot, the heroes feverishly work to free Merlin. Determined to help Emma, David embarks on a quest to retrieve a magical relic that Regina could use to communicate with the imprisoned sorcerer, but, when David leaves, Arthur insists on joining him because the dangers ahead are greater than he can imagine. Meanwhile, Mary Margaret discovers the fate of her old friend Lancelot. Back in Storybrooke, Arthur seeks David's help to catch a thief who threatens the safety of the citizens of Camelot. Across town, Emma reaches out to a conflicted Hook as she sets about her plan to draw Excalibur from the stone, on "Once Upon a Time," SUNDAY, OCTOBER 11 (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, Lana Parrilla as the Evil Queen/Regina, Josh Dallas as Prince Charming/David, Emilie de Ravin as Belle, Colin O'Donoghue as Hook, Jared S. Gilmore as Henry Mills, Sean Maguire as Robin Hood, Rebecca Mader as the Wicked Witch/Zelena and Robert Carlyle as Rumplestiltskin/Mr. Gold.

Guest stars include Lee Arenberg as Leroy/Grumpy, Beverley Elliott as Granny, Liam Garrigan as King Arthur, Joana Metrass as Guinevere, Sinqua Walls as Lancelot, David-Paul Grove as Doc, Gabe Khouth as Sneezy, Faustino Di Bauda as Sleepy, Michael Coleman as Happy, Mig Macario as Bashful, Jeffrey Kaiser as Dopey, and Giacomo Baessato as Grif.