Pretty much.

Giving a formulaic thriller a title like “Unforgettable” is an act of wishful thinking, but as middlebrow trash goes, this latest entry in the “psycho ex from hell” sub-genre isn’t bad. Or maybe it’s more accurate to say it’s no worse than it’s supposed to be? These Lifetime Channel-type movies thrive on a mixture of melodrama and camp, the charms of which often elude me.

Anyway, web publisher Julia Banks (Rosario Dawson) is engaged to nondescript perfect gentleman David Connover (Geoff Stults) and has just moved into his Southern California home with him and his young daughter, Lily (Isabella Kai Rice). Living nearby is David’s bitter ex-wife, an exacting, white-haired ice queen named Tessa (Katherine Heigl) who is cuckoo for cocoa puffs and uses her and David’s shared custody of Lily as an excuse to second-guess and undermine poor Julia.

But there’s another component here, and it’s a ripe, tacky one! A few years ago, Julia fled her abusive husband, Michael (Simon Kassianides, seen in aggressive flashbacks), and filed a restraining order against him that has recently expired, putting her in a nervous mood. Crazy Tessa discovers this and, by impersonating Julia online, plots to ruin Julia and David’s relationship by bringing Michael back into the picture. (Julia never told David about her past trauma, from which she has still emotional and physical scars. The movie pretends she keeps it from him for complicated psychological reasons, but really it’s so David can plausibly be confused and suspicious when evidence of “another man” starts popping up.)

Heigl, thanks to her reputation as a “difficult” actress and her knack for starring in terrible films (“27 Dresses,” “The Ugly Truth,” “Killers,” etc.), has taken her lumps in the last several years. But she’s well cast as Julia, who’s essentially a soap-opera villain, a caricature of feminine severity that’s part “Mommie Dearest” and part “Fatal Attraction” bunny-boiler. Heigl is smart to lean into this sort of role, her mien perfect for a character who drinks red wine in a dark room while plotting her rival’s demise. And Rosario Dawson? She’s fine.

But the film, directed by veteran producer Denise Di Novi and written by Christina Hodson (“Shut In”), is hindered by its refusal to be creative and unwillingness to surprise us. It begins with a flash-forward to Julia being interrogated by cops, showing her the dirty Facebook messages she exchanged with her abusive ex and accusing her of murder — so we already know what Tessa’s plan is before she carries it out. It’s also the frustrating type of movie where a crazy person tells insane lies that everyone believes because the innocent party doesn’t try hard enough to explain the truth. The dithering and gaslighting and poor communication make me impatient.

(P.S. You might be intrigued to see Cheryl Ladd playing Tessa’s mom or Whitney Cummings as Julia’s best friend, but don’t be.)

C- (1 hr., 40 min.; R, three F-words (plus a written one), some sexuality, brief partial nudity, moderate violence.)