The line in question: "The house had been holding its breath since the Marchetti girl disappeared, and now that Cora had moved in with her three boxes and her determined not-noticing, it exhaled."
I want old-house unease — the sense that a building has memory, that it has been waiting. I do not want the word horror to appear anywhere near the first fifty pages. The Marchetti girl is backstory. Cora's denial is the engine.
My worry is that the sentence is doing too much. The breath metaphor, the backstory drop, the character note, all in one go. A reader who likes atmosphere might settle into it. A reader who prefers a cleaner entry will feel handled.
Would you keep the rhythm? Lean it out? Or is the density the point — that Cora is walking into something already full?