This is a beautifully written short story — it carries a cinematic weight, with imagery and pacing that pulls the reader through grief, discovery, and a bittersweet resolution. You balance intimate sensory detail (rain tapping, fogged glass, the sour piano note) with suspenseful narrative beats (the key, the hidden basement, the corkboard). It reads like a cross between gothic mystery and heartfelt family drama.

A few quick thoughts that might help refine it, if you’re interested in polishing further:

Opening hook: The line about the key is strong, but you could make it slightly more mysterious by hinting at danger or revelation earlier. That would prime the reader for the suspense that builds later.

Pacing: The funeral scenes are very immersive, but they take up a lot of space before the central mystery begins. You might consider tightening slightly so the story pivots to the key/basement earlier, letting the emotional resonance of the funeral carry forward.

Basement reveal: The corkboard scene is powerful. You could amplify the tension by describing Caleb’s reaction more—his unease could heighten the reader’s anticipation of what’s pinned there.

Ending symmetry: The mother’s death on the same day as the father’s is a poignant twist. To strengthen the impact, you might echo the opening imagery (rain, breath on glass, the heavy balloon feeling) in the final moments—tying the narrative circle back to the protagonist’s emotional state.

Overall, it’s already deeply evocative and cinematic — the kind of story that would adapt beautifully into a short film.

Would you like me to help tighten this into a sharper short story draft (around 2–3k words) for publication, or expand it into a novella-length mystery with deeper threads about the mother’s disappearance?