“Gaslight” meets “Memento” in “Before I Go to Sleep,” a lethargic, very silly would-be thriller adapted by Roland Joffe from S.J. Watson’s novel. It also features scenes of abuse that are remarkably nasty and protracted, but still aren’t enough to keep one from dozing off as it unspools at an alarmingly slow rate.

The protagonist is Christine Lucas (Nicole Kidman), who’s introduce to us waking up one morning blank-eyed and puzzled—Joffe loves close-ups of her bloodshot peepers—only to be informed by her husband Ben (Colin Firth) that she has suffered for years from psychogenic or dissociative amnesia that causes her memory to go completely dark each day, forgetting even the experiences of the previous one. Ben tells her that the condition was the result of a car crash, and assures her of his continuing love and devotion.

What Ben doesn’t know—but we’re quickly told—is that for some time Christine has been working with a neuro-psychologist named Nash (Mark Strong), who calls every morning to remind her to consult a video diary from the previous day that she’s been assiduously keeping under his guidance. The process allows her to begin each morning from a somewhat less empty perspective and gradually expand on what she can remember. It also reveals elements of her past that Ben has been keeping from her—the fact that they had a son who died young of meningitis, the existence of a close friend with red hair. And it brings terrifying, jumbled visions of an assault—not an auto accident—that caused her amnesia, though the fractured images don’t allow her to discern who was delivering the blows.

All of this gradually raises issues in Catherine’s mind about how much she can trust Ben, and whether he has her best interests at heart. But it also makes her suspect that Nash might have sinister motives. As she ventures out more and contacts other people, her memory improves but the uncertainty increases, just as she’s about to go off with Ben on an anniversary holiday. Needless to say, all is eventually revealed in an ending that’s part unpleasant violence and part pallid tearjerker.

This sort of helpless damsel-in-distress stuff has been done to death over the years, with Hitchcock alone using it as a vehicle for both Joan Fontaine in “Suspicion” and Grace Kelly in “Dial M for Murder.” (Of course, it’s a subtext to “Vertigo” as well.) But in addition to Ingrid Bergman in “Gaslight,” one can recall actresses as different as Barbara Stanwyck and Doris Day involved in such claptrap, the former in “Sorry, Wrong Number” and the latter twice, in “Julie” and “Midnight Lace.” Kidman’s contribution to the genre is close to the bottom of the heap (though it’s difficult to go lower than the two Day examples). Part of the problem lies with her mechanical performance, but much of the blame must be borne by Joffe, a serious fellow who seems totally out of synch with this sort of pulpy material. Unlike Christopher Nolan, who directed “Memento” like a house afire, Joffe goes the slow, ponderous route, resulting in a picture that’s unforgivably lugubrious despite its brief hour-and-a-half running-time. And, of course, the deliberate pacing makes it feel all the more ridiculous.

Nobody else in the cast distinguishes himself either. Firth furrows his brow and looks angst-ridden throughout, while Strong is robotically impassive. Particularly inept turns are handed in by Adam Levy and Dean-Charles Chapman, both of whom turn up toward the close and offer line readings that sound as though they were being spoken phonetically. The technical side of things is better. Kave Quinn’s production design and Ben Davis’ cinematography—along with lots of good old English rain—add a bit of atmosphere to what’s otherwise an uninspired slog.

The best thing about “Before I Go to Sleep” is that you don’t have to suffer from amnesia for it to be eminently forgettable. Suffering through the movie is quite enough.