Is it a spoiler to refer to the coda of thriller “The Boy” as the clumsiest cop out in recent horror history?

Never mind.

That goes for the movie as well, a tepid tale of elderly Brits, the Heelshires (Diana Hardcastle, Jim Norton) who hire, sight-unseen, a young American Greta (Laurent Cohan) as nanny to their little boy.

But “The Boy” is a life-size porcelain doll, which you know if you’ve seen the TV ads or the theatrical trailers. So our struggle is the same as Greta’s — to not laugh.

The boy’s name is Brahms, and yes, he loves “Brahms’ Lullaby.” Brahms has rules. Music “is to be played, loud.” He has to be dressed for bed and kissed good night. He must be read to “in a loud, clear voice.”

Never leave Brahms alone. Never cover his face. Never, ever spill water on him.

Oh wait, that’s “Gremlins.”

Greta, of course, is ready to ignore that long list of orders when the elderly couple leaves them alone together. And that’s when things turn weird.

Rupert Evans is Malcolm, the flirtatious grocer who tries to make time with Greta even as he wonders if she’s going off her rocker. Greta starts to believe Brahms is real.

It’s as if she followed Mr. Heelshire’s own trip down the rabbit hole of delusion.

“Little by little, and then, all at once.”

She believes!

The doll is creepy by design, but director William Brent Bell (“The Devil Inside”) can’t do much with him that surprises us, much less frightens. The sound design — chilling noises, music, footsteps heard over our shoulders — works.

At least the lovely Ms. Cohan looks alarmed — wild-eyed, once or twice. But even she loses her fear of the doll. Long after we have.

MPAA Rating:PG-13 for violence and terror, and for some thematic material

Cast: Lauren Cohan, Rupert Evans, Diana Hardcastle, Jim Norton
Credits: Directed by William Brent Bell, script by Stacey Menear . An STX release.

Running time: 1:37