Is "Lights Out" the story of an evil supernatural entity unable to rest after her untimely death, or is it a piercing metaphor for the ravages of mental illness? Director David F. Sandberg's debut feature (based on his 2013 short film) works on both levels, but it is this latter thematic undercurrent which separates the film from its routine brethren. It doesn't hurt that the spectral heavy is played by an obscured yet seamlessly tactile live-action actor rather than an overtly CG-augmented creation. This achieved authenticity heightens the admittedly predictable spook tactics, just as the committed actors bring added depth to otherwise underwritten characters in Eric Heisserer's (2011's "Final Destination 5") no-fuss screenplay.

When twenty-something Rebecca (Teresa Palmer) receives a call from younger half-brother Martin's (Gabriel Bateman) school about his sleeping in class, it is a surefire sign mother Sophie's (Maria Bello) depression and possible schizophrenia have reared their heads in a big way. Grieving over the recent mysterious death of second husband Paul (Billy Burke), Sophie is up all hours of the night, speaking to an unseen friend she calls Diana. Rebecca knows all too well about Diana, a presumed figment of Sophie's illness who haunted her nights as a child. Worried their mom has stopped taking her medication, Rebecca welcomes Martin into her home. Simply going across town, however, is not enough to save them from a sharp-clawed, light-sensitive wraith who is much realer than a mere voice in Sophie's head.

Running a fleet 81 minutes, "Lights Out" wastes no time jumping into its malevolent goings-on. Pared down to what feels like its bare essentials, the narrative achieves its top goal of casting an atmospheric pall and putting the viewer on edge. When so many movies of this kind lose their mojo the moment revelations come to light over the identity and motive of their appointed villain, Diana escalates in intimidation as more is learned about her and her unhealthy connection to Sophie. While Diana is real enough for others to ultimately be able to see her, director David F. Stanberg provocatively suggests her power is being fed by Sophie's tortured, deteriorating mind—a dichotomy cast in ambiguous shadows. Indeed, more serious issues beyond the wrath of a territorial ghost are afoot.

For a heroine who has only been given breadcrumbs of development, Teresa Palmer (2016's "The Choice") is superb as Rebecca. She lives on her own in a one-bedroom apartment, is hesitant over committing to sort-of boyfriend Bret (Alexander DiPersia), suspects she has been kept in the dark over her father's whereabouts, and holds a strained relationship with mom Sophie. Beyond this, not much is learned about her, including what she does for a living (early on, she mentions she has to get up early for work, but no specific job is ever established). Palmer plays the sympathetic Rebecca without artifice; she feels like a real person, one who chooses to take responsibility for her brother as Sophie's behavior grows erratic.

As mother Sophie, Maria Bello (2013's "Prisoners") brings a conflicted emotional intensity to her beleaguered character, a woman who knows she is in trouble but isn't sure how to escape the control of someone who refuses to loosen her hold over her. Not unlike the quality Haley Joel Osment brought to 1999's "The Sixth Sense," Gabriel Bateman (2014's "Annabelle") displays a thoughtfulness belying his young age as Martin. Alexander DiPersia (2008's "An American Carol") excels as Rebecca's semi-love interest Bret the more the viewer gets to know him; at the start, he appears to be rough around the edges and untrustworthy, but he quickly proves to be exactly the opposite, supporting Rebecca and Martin in their time of need and—shocker—actually believing them about Diana. Finally, the physical command of actor and stuntperson Alicia Vela-Bailey's body movements proves a chillingly indelible asset for bringing Diana to menacing life.

"Lights Out" adeptly weaves a web of tense, nightmarish situations undercut on occasion by blips in logic. The core plot hook—that the supernatural antagonist is only powerful when the lights are off—opens itself to plenty of teasing scenes where lightbulbs flicker and candles act as weak protection in threateningly dim surroundings. Other parts, however, frustrate as characters who are well aware they must remain illuminated walk around lonesome houses and don't bother to even try to flip on a lightswitch. The general premise isn't new, either; while certainly effective, it is nearly identical to the one used in 2003's killer tooth fairy thriller "Darkness Falls." As a fright flick specializing in suspense over violence and suggestion over too much lugubrious exposition, the film works in spite of its trouble spots. Rebecca and Martin are resourceful, root-worthy siblings, their oppressed relationships with their ailing mother leading to a few grievously potent confrontations. "Lights Out" steadfastly follows them toward a resolution as uncompromising as it is inevitable. To save each other, all three family members have but one choice: to face their fears head on, no matter the sacrifice.