Once Upon a Time season 5
Emma as Dark One in Once Upon a Time season 5 ABC

Mary Margaret aka Snow White will have to take things in her own hand, as Lancelot has warned her of King Arthur's true intentions in the upcoming episode of Once Upon a Time season 5. Episode 4 is titled, The Broken Kingdom, where Dark Emma will unleash a secret weapon in her plan to find "the brave soul", as she needs to draw the Excalibur from the stone.

The official synopsis of the episode reads as follows:

Click here to watch it via live stream online on ABC, or click here to watch it online on ABC's official website.

King Arthur's real intentions will be revealed in the episode as a new promo shows Arthur telling David, "For years I have hunted the missing piece, something known as the Dagger of the Dark One."

Then, David tells Snow, "Arthur has a way to use that to help Emma." However, she is of the view that Arthur cannot be trusted. And then, Snow can be seen teaming up with Lancelot to hide the dagger from Arthur, as the promo ends with him pointing his sword at Snow, and saying: "You are going to hand over that Dagger."

Meanwhile, Dark Emma begins the second phase of her plan, by unleashes a secret weapon to find the brave soul, who will draw the Excalibur from the stone.

OUAT season 5 episode 4 airs this Sunday, 18 October at 8pm EST on ABC Network.