Mark our words: Rose Leslie and Harry Treadaway will be household names in due time. For detail-oriented fans of cable TV dramas, they're probably already instantly recognizable. On HBO's Game of Thrones, Leslie played Ygritte, the wildling badass with a soft spot for one Jon Snow, even though he "knows nothing"; Treadaway, meanwhile, is Dr. Victor Frankenstein on Showtime's delightfully audacious Gothic horror series Penny Dreadful.

On September 12, their fictional union will be a genre's fan pleasure. Leslie and Treadaway play a newlywed couple in Honeymoon, writer-director Leigh Janiak's hugely impressive feature film debut. One of our favorite movies out of SXSW this year, Honeymoon follows their characters as their relationship crumbles, no thanks to, let's just say, "supernatural" forces. The descent happens once Bea (Leslie) and Paul (Treadaway) get settled into a secluded cabin that she once frequented as a youngster; there, during one bizarre night, Paul finds Bea out in the woods, naked and disoriented, and that strange incident triggers her mental and physical deterioration and his reluctant detective efforts, all of which collide in Honeymoon's unnerving finale.

Honeymoon, in addition to giving Leslie and Treadaway a fittingly strong movie in which to shine, is also the official coming-out party for Leigh Janiak as a filmmaker to watch. With strong characters, unpredictability, and an oppressively eerie and dread-lathered atmosphere, Honeymoon feels like the work of an accomplished scary movie veteran, not a rookie.

Clearly, we're big fans of Honeymoon and Janiak around here, so this right here is quite the treat: Thanks to the good folks at Magnet Releasing, the film's distribution company, we've landed the exclusive premiere of Honeymoon's striking teaser poster. Give it a look below, and be sure to seek Honeymoon out when it opens theatrically and hits iTunes and VOD on September 12. It's the kind of unexpected surprise that horror movie fans live for—not to mention, quintessential Permanent Midnight material.