It takes a villain to catch a villain.

Or at least that's the working theory when Regina goes undercover to infiltrate the Queens of Darkness on Once Upon a Time this Sunday.

But will she be able to convince them that she's embraced her dark side once again? Can Regina manage to play around with evil without being tempted back to black magic? And can Emma, David and Mary Margaret keep an eye on her while she's undercover?

Elsewhere, Hook has a special request to make of Belle but she may have a different conversation in mind as she holds an impromptu meeting with both Hook and Will Scarlett. Does this have to do with Mr. Gold or is there something else on her mind?

Check out these photos from Once Upon a Time Season 4 Episode 15, "Enter the Dragon," which is scheduled to air on Sunday, March 15 on ABC at 8/7c.