Fern Laguire was Quinton's supervisor at the National Security Agency (NSA) at Fort Meade. Quinton was on loan to Fern's group when he started to have misgivings about spying on Americans. He wanted out and Fern would not let him go. She isn't homocidal (i.e., she would let people leave the agency so long as the appropriate monitors and security were in place), but Quinton wanted to leave without those monitors--he wanted true freedom. So he left without saying he was quitting.
He slipped through Fern's security measures making her look fallible. She needs to retrieve Quinton and bring him back to the NSA to save face. Additionally, as she's close to retirement, if she doesn't cross all her T's and dot all her I's, when she retires she'll be treated the same way as everyone who retired under her--as less than free, with security and monitoring 24/7. She does not want that so she has been hunting Quinton since he slipped away from the NSA. (Underground, p. 275.)