‘Once Upon a Time’ Season 5, episode 4 spoilers: Promo video teases on the dagger and King Arthur’s betrayal [WATCH]

Actors Ginnifer Goodwin And Josh Dallas, Right, From The TV series 'Once Upon A Time.' — Actors Ginnifer Goodwin and Josh Dallas (R) from the TV series "Once Upon A Time&" arrive at the 15th Annual Costume Designers Guild Awards in Beverly Hills February 19, 2013. Reuters

Lancelot (Sinqua Walls) has returned in “Once Upon a Time” Season 5 to warn the Storybrooke heroes about King Arthur (Liam Garrigan). A promo video for “Once Upon a Time” Season 5, episode 4 titled “The Broken Kingdom” teases that the Camelot ruler is slowly revealing his true intentions involving the Dark One’s dagger.

Spoiler Alert: This feature contains major “Once Upon a Time” Season 5 spoilers.

According to the new episode’s brief synopsis in a Comic Book report, the dagger is the one possession that can beat the darkness in Emma Swan (Jennifer Morrison), the new Dark One. However, the weapon will stand between Emma’s parents Snow White/Mary Margaret (Ginnifer Goodwin) and Prince Charming/David (Josh Dallas) as well as their plan of saving their daughter.

Snow White, who holds the Dark One’s dagger in the promo video, declares that the Storybrooke heroes must hide the weapon from the threat. Snow White also warns her husband Prince Charming that they cannot trust King Arthur, who wants to find the Dark One’s dagger so that his Excalibur sword will be whole again.

It is further teased that “Once Upon a Time” Season 5, episode 4 will feature on the unlikely team-up of Captain Hook (Colin O’Donoghue), Robin Hood (Sean Maguire) and Regina Mills/Evil Queen (Lana Parrilla). In the previous episode titled “Siege Perilous,” Hook wants to find out what Emma is hiding in the basement of her house so he enlists the help of Robin Hood.

The Storybrooke heroes are still unaware that Emma has been keeping King Arthur’s Excalibur sword since they returned from Camelot. Emma also wants to make the Excalibur sword whole again and use the weapon to snuff out the light.

Emma tried to pull the sword herself but the previous Dark One Rumplestiltskin (Robert Carlyle) informed her that only a hero can do that. Emma has brought Mr. Gold (Robert Carlyle) back from his comatose condition in order to fulfill her plan involving the Excalibur sword.

Emma wants Mr. Gold to be the hero that she needs in pulling out the important weapon. “Once Upon a Time” Season 5 returns with episode 4 titled “The Broken Kingdom” on Sunday night, Oct. 18, at 8/7c on ABC.

Watch the “Once Upon a Time 5x04 Promo ‘The Broken Kingdom’ (HD)” video: