The Killing — Robert Muchamore

CHERUB agents are all seventeen and under. They wear skate tees and hemp, and look like regular kids. But they're not. They are trained professionals who are sent out on missions to spy on terrorists and international drug dealers. CHERUB agents hack into computers, bug entire houses, and download crucial documents. It is a highly dangerous job. For their safety, these agents DO NOT EXIST.

Leon is a small-time crook with big money. When the cops call in CHERUB, James's mission looks entirely routine: make nice with Leon's kids, dig up some leads, and infiltrate his home. But when James suddenly unravels a much larger plot, the mission becomes anything but ordinary. Unfortunately, the only person who might know the truth is a reclusive eighteen-year-old boy -- who happens to have died more than a year ago.