Meet my Hatchet of Death (or, some other colorful description RC Lewis and I come up with at any given moment). This is how I edit myself, it is how I edit others. If you think you want to play with me and my hatchet, shoot us an email.
We all know the first line of a query is your "hook." I call the last line the "sinker." You want it to punch them in the face, in a nice, friendly kind of way that makes them unable to forget you after having read the 300 other queries in their inbox.
If you're looking for query advice, but are slightly intimidated by my claws, blade, or just my rolling googly-eyes, check out the query critique boards over at AgentQueryConnect. This is where I got my start, with advice from people smarter than me. Don't be afraid to ask for help with the most critical first step of your writing journey - the query. My comments appear in green.
When Violet Gloom and her brokenhearted dad pack everything up and move to the dreary town of Downcast, she’s pretty sure that she’s left the happiness of her old life behind in the dust. Sightly mixed metaphors here with "dreary" and "dust," plus the hook is a little long in the tooth - but it's not bad. But when she finds a ghost lurking in her new house, she discovers a secret: Downcast is cursed. The "but" here implies that the sentence will be at odds with what came before, however leaving the happiness of her old life behind and finding out the town she moved to is cursed aren't disagreeing with each other. Three hundred years before, a young witch cursed Downcast to eternal sadness and eventual doom, why? and now on the anniversary of the curse, that doom is nigh. Violet has just three days to get the ghosts to the Great Beyond What does this mean and how would she do that? and stop the curse, or she, her dad and the entire populace of Downcast will be destroyed by ghosts-gone-bad, otherwise known as shadows.
With the help of Henry Fair-Weather (a boy who’s allergic to magic) how does that impact the plot and what is his role? and her cat Dusk how does she fit in? , Violet sets out to break the curse how? , find a home thought she had a new one?, defeat an evil ghost-obsessed inventor this sounds like an important plot point that we need to hear more about in the body and cure her family’s sadness. VIOLET GLOOM AND THE CURSE OF DOWNCAST is complete at 48,000 words.
Right now this reads like any other haunted house / town story. We've got a hero whose responsibility it is to save her home / family / town, with a (possible love interest?) boy. But I have don't know how she would do this, and I only have tiny hints about why this story is different from all the others. I feel like the inventor could be the answer to that, but I know nothing about him. And what about the cat? How is it helping? Can it talk? You need to elaborate on your cast of supporting characters, and you also need to clarify your age range here. I'm assuming by the word count that it's an MG, but you don't specifically say that.