This 'Oculus' Exclusive Clip Will Scare The Crap Out Of You

'Doctor Who' vet Karen Gillan stalks a haunting mirror in our SXSW Fest sneak peek.

Mirror, mirror, on the wall — which sneak-peek movie clip is scariest of them all?

The answer is right here, if you're brave enough to look. We have an exclusive first look at a scene from Relativity Media and director Mike Flanagan's upcoming thriller, "Oculus," ahead of its upcoming South by Southwest debut.

"Oculus" stars Katee Sackhoff and Karen Gillan, best known to genre fans for their work as Starbuck on "Battlestar Galactica" and Amy Pond on "Doctor Who," respectively. Here, the two leading ladies are getting into a scarier game. Gillan plays Kaylie Russell, whose life was changed forever when her brother Tim (Brenton Thwaites) was convicted of killing their parents many years ago. But Kaylie knows better; she knows that it wasn't Tim, but a supernatural force, that was responsible for her parents' deaths — and she's determined to prove it.

How does that supernatural force operate, you ask? That question gets addressed in our exclusive clip, which sees Kaylie walking in a dreamlike state toward a large, haunting mirror. The pulse quickens as Kaylie draws nearer and nearer and nearer to the mirror, until finally...

...yeah, like we're going to spoil the surprise. Watch the clip and try not to jump out of your seat; we dare you.

"Oculus" arrives in theaters on April 11, and will also appear at the SXSW Festival as part of the horror-studded midnight lineup. Prepare your nerves accordingly, and try to stay away from mirrors.

Tell us what you think of "Oculus" in the comments below!