** SPOILERS **
Teresa Palmer and her younger half-brother Gabriel Bateman have their lives ruined by their mother Maria Bello's evil imaginary friend in Lights Out. Having left home under muddled circumstances, Palmer must confront her family's past when her little brother begins having the same experiences she had growing up: seeing shadowy apparitions, hearing scratching noises in the dark, and finding the name "Diana" scrawled on the wooden floors. Oh, and also being attacked and having a crazy shadow lady try to kill him. "Diana" is the name of the wraith in question, kind of a cross between the evil girl in The Ring and Wolverine in silhouette, plus a number of other derivative monsters of the modern scary movie genre. In an effective opening sequence, Diana murders Billy Burke, young Bateman's father and current husband to Bello, who has a lifelong history of mental illness. Ultimately, all this means Palmer, Bateman, and her loyal mensch of a not-quite-boyfriend Alexander DiPersia, must spend a night in Bello's haunted house to get to the bottom of how to kill Diana.
Lights Out plays fast and loose with Diana's vulnerability to light. We learn via info dump -- which is literally Palmer walking into a room of her mom's house and finding boxes of files conveniently detailing everything she needs to know -- that Diana and Bello were childhood friends in a mental institution. (Bello was hospitalized for "depression" and befriended Diana, who has a bizarre skin condition making her vulnerable to light. Oh, also she's an evil murderer who killed her father.) Diana died in an operation to cure her of her skin condition, but was reborn as a ghost who haunts Bello, keeps her crazy by making her not take her meds, and occasionally declares war on her family. Under these bizarre circumstances, Bello's loyalty to Diana is laughable. Diana's hauntings aren't confined to Bello's creepy home with its unusually enormous basement, however. She can go on field trips at will, attacking Burke in his factory workplace, and showing up at Palmer's apartment. And yet, any amount of light like candle light, a flashlight, black light, or even the LED of an iPhone can keep Diana at bay momentarily. What about Pop Rocks? If you crunch Pop Rocks in your mouth and they make sparks, will that keep Diana at bay?
Though Lights Out is creaky with its own rules and reveals, and the movie displays about as much understanding of mental illness as a Daredevil movie understands about trial law, it does better with being clear about how child protective services works, and what Palmer would have to do if she wanted to contest her crazy mom and claim legal guardianship of her little brother. Palmer anchors the tidy horror of Lights Out with determination and conviction. Palmer's desire to protect her younger brother is admirable and makes for one of the better sibling relationships in the modern horror genre. DiPersia, as Palmer's love interest Bret, is surprisingly loyal and upstanding. All he wanted was to be able to keep some stuff in her apartment (he negotiates down to one sock) and ease her off from being such a commitment-phobe, DiPersia is a solid dude for hanging in there and facing all this crazy and murder when other guys would have turned tail and ran. In the end, it was cool to see Palmer bet her bottom drawer on DiPersia and win. Though Palmer and her brother would probably have been safe if they sought shelter in a Motel 6; their famous slogan is "We'll Leave The Light On For You."