'Once Upon a Time' season 6 episode 12 spoilers: Regina discovers Robin's dark side; Gideon's origin story to be featured

Robin Hood (Sean Maguire) has come to Storybrooke with Regina (Lana Parilla), but the once Evil Queen will soon find out that her beloved has a dark side himself. Meanwhile, the origin stories of Gideon (Giles Matthey) and the Black Fairy (Jaime Murray) will be featured in later episodes.

On the next episode of "Once Upon a Time" season 6, titled "Murder Most Foul," Regina will help Robin in adapting to his new life in Storybrooke. In the process of starting fresh, Regina will find out that her beloved has a dark side.

"Regina works to acclimate Robin to life in Storybrooke, but soon discovers he has a dark side that makes the task much more complicated than she anticipated," the episode's listing on The Futon Critic reads.

However, Hook (Colin O'Donoghue) will have the opposite situation.

The captain pirate will try to prove to David (Josh Dallas) that he's more than just an untrustworthy pirate, "So when David asks Hook to help him uncover the truth about his father's death, Hook agrees."

Meanwhile, executive producers Adam Horowitz and Edward Kitsis shared with E! News that Gideon and the Black Fairy will have their origin stories tackled later on in "Once Upon a Time" season 6.

It seems that Gideon's backstory will reveal why he wants to be the Savior himself. And since his intentions have something to do with the dark realm, the Black Fairy's origin story will also be a piece of the bigger puzzle.

"What I can tell you is that he hinted at wanting to free the realm of the Black Fairy. His motivations are going to become clearer in his origin story and the Black Fairy's origin story, which is two flashbacks we'll be doing this year," Kitsis revealed.

"Once Upon a Time" season 6 airs every Sunday night at 8 p.m. ET on ABC.