But while these start as flashbacks, they increasingly become very much here and now as Kaylie and Tim's perceptions start blending the two together, courtesy of a mirror that has a very Dr. Manhattan way of seeing all of time at once. For the longest time, the film tries to hedge its bets between "are they crazy" and "no, there really is a bad mirror," but by the time ghosts of the previous owners are appearing, it's clearly in the latter camp.
The film's most problematic issue rears its head towards the very end, and I'm going to mention it without describing any particular plot points. It is this: once you start blurring the lines between fantasy and reality, there has to be some kind of indication what's what, an Inception-style totem, if you like. Because if we get to the point where we cannot believe anything we're seeing, at some stage we'll lose a compelling reason to identify with it. And if you're not rooting for the potential victims in a horror movie, it ceases to scare. Arguably, Flanagan has built himself such a house of cards at this point that there's nothing to do but make it collapse - by the time you get there, it's hard to think of an ending that would be truly satisfactory.
The director's work with his cast is better. If you didn't know, for example, that the grumbling, creepy father was once stoned Slater from Dazed and Confused, you'd never guess. Sackhoff goes the furthest, though, in a dual role as both the nice mom beaten down into a monster, and her mirror-eyed doppelganger form inside the reflective otherworld. Shedding all vanity as a great actor should, she can make you want to be embraced in her arms one moment, and run screaming the next (given the timeline-blurring, those moments do often happen right next to one another). Gillan, as mentioned before, carries the movie, as she must - this is Kaylie's story, and her obsessive-compulsive way of dealing with everything. Her strength and decisiveness is an asset at first, but increasingly a detriment as her certainty cannot be trusted, and Gillan maintains the arc wonderfully. Thwaites, yeah, he's a stiff at first, but he does gradually become adequate.
But oh, that ending - it got quite a few groans at my screening. Are you willing to put up with an otherwise excellent frightfest even if it limps to that finish line after sprinting for an hour-plus?
(Don't worry about the WWE Studios logo, though. It is light years beyond anything else with that name attached, and I say this as somebody who enjoyed the first Marine with John Cena.)