Ruth Platt’s “Martyr’s Lane” is horror at a low simmer, a triumph of tone over content, performances over frights.

This beautifully Gothic ghost story rests on the shoulders of two angelic moppets, a film that makes its myopic simplicity a virtue in every perfectly-composed frame.

Kiera Thompson plays Leah, a parson’s daughter living in the eerie rectory provided by her father’s parish. She keeps to herself and plays alone. But there are voices in this house, and Leah hears them. And there’s something haunting her mother (Denise Gough of “71,” “A Dark Place” and “The Kid Who Would Be King”) that may or may not be related to the whispers Leah hears in the shadows.

Leah’s cruel college-bound sister Bex (Hannah Rae) makes sure to add the spooky story of how they live down the street from an old monastery that was the scene of a Catholic massacre in the Church of England’s violent birth years to her teasing and tormenting routine. Bex sees the worst in the kid, even in Leah’s asthma attacks.

“You’re an attention-seeking little brat,” she hisses.

Father Thomas (Thomas Cree) is devoted to his parish, and popular. But wife Sarah sees the nuisance the older women parishioners are, bridling at the bossy fussbudget (Anastasia Hille) who’s always going on about the books and “receipts.”

All of them are too busy for Leah, whose curiosity has her wondering what she’s hearing and coveting what Mum has hidden away in her locket.

That’s about the time that the late night visits begin. The little girl (Sienna Sayer) is dressed in a battered white outfit, with wings clipped on. She can’t recall her name, but calls herself Leah’s “guardian angel.” And in their giggling games and chats, she challenges Leah to find this or that item lost or buried on the church grounds.

We adults know that those are “clues,” clues with a hint of menace about them.

Thompson and Sayer’s scenes are a moppet-sized marvel, natural, polished, perfectly-enunciated — empathetic acting at its most natural. They’re a big reason this picture, which has a guessable “mystery” and a lot more lowering gloom and dread than frights, comes off.

Leah’s travels make us fear for her. And the fact the family has a pet dog and a white rabbit Leah’s named “Mary” because it somehow got pregnant locked up in a rabbit hutch make us wonder what other grimness awaits.

Actress turned writer-director Platt (“The Black Forest”) draws us in and serves up just enough foreboding to keep us engrossed. There’s not a lot here, but the well-crafted minimalism and occasional moving moment pay off.

“Martyr’s Lane” is a reminder that you don’t need entrails and screams, demons and cadavers to cast a ghostly spell. Sometimes, a weathered abandoned doll in a fall-cluttered English garden, a lock of hair or faint scratching at a window is all it takes.

Rating: unrated, mild horror violence

Cast: Kiera Thompson, Denise Gough, Sienna Sayer, Thomas Cree and Hannah Rae.

Credits: Scripted and directed by Ruth Platt. A Shudder release.

Running time: 1:36