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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.
All hope is never lost. Not even in Nowhere. Decent hook. I like it. Nice and concise.
Cerulean and Amarillo Saffron are sisters separated by guilt, regret, and a secret the Ardor Laboratory Corporation will go to any lengths to protect. Again, this is a good starter sentence. Their names are a little tongue triply, but if those are their names then that's the case. Only hope can reunite them and save the Lost Children of Nowhere. Now you are getting pretty vague, this is actually a decent sinker to put at the end, but right now I don't know if Nowhere is a real town, a secret location, or even if we're talking about Earth here. Amarillo hasn't seen her baby sister since the day she disappeared from their family home nine years ago. So is Cerulean only 9 years old? Or do you mean just "little" sister? A chance assignment given to her by her boss Boss? So how old is Amarillo that she has a job?, Mayor Naples Orange of Somewhere, proves to Amarillo that there was nothing she could have done all those years ago to protect Cerulean. It also gives the spunky young woman definitely need to say how old she is, or give an indication something else she sorely needs--hope that it is still possible to save her sister, and all the other Lost Children who are trapped in the neighboring city of Nowhere. I definitely think you need to clarify whether this is set on Earth, a future version of Earth, or somewhere else entirely.
To save the Lost Children, Amarillo has to get inside Nowhere. That is no small feat. No one in Somewhere can remember anyone ever being able to get in or out of their sister city, except maybe Nowhere's mayor, the boogeyman Mayor Blue. If no one has even been there, or gotten in or out, how do they know who the mayor is, or that the children are there? But Amarillo knows she can do it, even if she has to do it alone. Mayor Orange is busy with his pet road project, the Roy G. Biv highway that will connect Somewhere and Nowhere and hopefully spur economic growth. Why would it spur economic growth if no one ever goes in or out? Also there is the issue of the continued hope theft from the emotion recycling plant. This subplot here comes out of nowhere, and firmly lands this in the realm of sci-fi, or at least speculative fiction. At first Amarillo thinks she may be able to turn to Deputy Mayor Scarlet for help, but when she spots him inside Nowhere--on the other side of the seemingly impenetrable force field that seals that city off from the rest of the world--with an armload of stolen emotion actuators, she knows he is up to no good. I feel like there's a lot going on here, and no real indication of what our MC wants - to get into Nowhere and get her sister out? But how does she know she's there, and why is she so certain she can do it? And how does the subplot actually connect with the main plot?
What is Somewhere's deputy mayor doing? Maybe it has something to do with The Outlawz, the elusive gang of saboteurs who have been attacking the road construction from the very beginning. Both Mayor Orange and the Somewhere Times have surmised that The Outlawz are probably a youth gang comprised of Lost Children. No one has any suggestions about what the saboteurs' motives might be, but when Amarillo sees Deputy Scarlet inside Nowhere with the pilfered hope, she gets an idea. What's the idea? Why would hope and the highway be connected? And why would anyone believe that the Outlawz are Lost Children if they think no one can get in or out of Nowhere? And why would lost children want to sabotage the road?
The more Amarillo digs into the problem of the Lost Children, the more she realizes it's not just a Nowhere issue. The histories of Nowhere and Somewhere are inextricably connected, and they are tied to the secret that the Ardor Labs Corporation You mentioned them in the beginning, in connection with the little sister and a secret, but now they come up again in connection with the highway, so this is kind of confusing --the largest employer in Somewhere and the biggest supporter of the Roy G. Biv highway--will do anything to keep buried. Amarillo finds an ally in Somewhere Times reporter Fern Viridian, and together, they--along with Mayor Orange--fight to unravel that secret and free the Lost Children. There are a LOT of names being mentioned in this query. You want to avoid that, especially when they are all different shades of color and potentially confusing. Earlier you said that our MC was going to do this alone, and now she's teaming up with two adults?
What Amarillo doesn't know is that the Lost Children have not been sitting passively by, waiting to be rescued. She should though, shouldn't she? If everyone suspects the Outlawz are Lost Children then it shouldn't be a huge surprise. Led by her intrepid little sister Cerulean and former Outlawz members Azure and Denim, they have been fighting: against the other Outlawz, So there's faction fighting among rebels? against Deputy Mayor Scarlet, and even against the evil Mayor Blue. When the battle finally unites the forces from Somewhere and the forces from Nowhere, they are ready to stand together and vanquish their foes with their strength and their hope restored. Except, honestly at this point I'm pretty confused about who is friend or foe, and what exactly the point was in the first place. You hint at a big secret that a corporation wants buried, and it has something to do with a road and possibly disappearing children but I'm not entirely sure on that last point. There are WAY too many names being mentioned in this query, it's highly confusing and reads more like a synopsis than a query.
You need to keep your query word count low - around 300 words. Don't name so many characters - stick to your prime movers and focus on the main plot point. Right now you've got a lot going on in this query - so much so that it will lead an agent to wonder if your novel is just as convoluted and confusing.
ROAD TO NOWHERE, a young adult urban fantasy novel, is complete at just over 77,000 words. I'm not sure that it is urban fantasy - UF is typically set in a recognizable place, with magical or SF elements. This seems like it's somewhere else entirely, or at least in the future.