Laura Bishop has a secret and she's the last person in the City still capable of keeping them. (I know this line originated from a suggestion I made a few rounds of critique ago, but I actually think that your next sentence is a superior opening line. "Laura Bishop is targeted by the government because she's the only person immune to their brainwashing drug".
If you do decide to keep your original hook, I actually like it better with the semi-colon. Or, more accurately, do replace the semi-colon with a dash. I:E. ...secret--she's the last person in the City capable of keeping them". Do what you like, you'll notice that feedback frequently contradicts. In short, you're never going to have a universally loved query, you just need to get to the point where you love it enough that the feedback isn't resonating anymore. )
Her immunity to Vocacium, a government-controlled brainwashing drug, makes her a target. She hides with the
Circuit, who are (avoid proper names unless you need them)a group of mercenaries hidden in the City's Underworld. Their sole purpose is to bring down the authoritarian government that rules the nation with an iron-fist. Laura’s past and knowledge of the drug makes her a useful asset. This is kind of clunky, you can pull it and no one's the wiser.
The Circuit suddenly Laura jeapordizes her group risks exposure when, during a failed terrorist attack, Laura when she is spotted next to the corpses of two civilians during a failed terrorist attack. She seeks help from an old friend who offers her protection in exchange for a favour – she needs to steal a valuable flash drive. When she discovers it contains proof of a fatal pathogen used in routine vaccinations on almost every citizen, she keeps it for herself.
Laura comes up with a plan. Instead of hiding, she Laura allows herself to be captured by Detective Jonah Nolan who’s been hunting her for months. She needs someone on the inside to hopes he will help prove the fatal nature of the pathogen, but the authorities have tasked Jonah with Laura's execution. To succeed Laura needs must convince Jonah to willingly betray the government that gives him power, or she’ll have to be buried along with the knowledge that could save the life lives of millions.
The bones are better, there's just a lot of wording tweaks I'd recommend to increase clarity and help it read smoother. My big concern is that there's just too much going on here. First she's with the Circuit, then she's working for that one guy, then she has the flashdrive, and finally she's captured by the detective. It's almost more of a synopsis than a query. If you can trim out her leaving the circuit and her work with that random guy and go straight from the mercs to the flashdrive, it'll be less events and more crisp. I also have this big question mark as to what the government could gain by comitting mass genocide. People in power need underlings, after all.
Hope this helps! Good luck and happy writing.
-I critique because I care.