I used to think that writers worked alone, sweating out their vision with nary a word to another human. Happily, I was wrong. This book wouldn't exist without help from a number of people.

Any author who doesn't first thank their agent clearly needs a new agent – or at least doesn't have mine. Deepest thanks to Scott Miller, a good friend and a remarkable advocate. Onward and upward, bro.

While most books have one editor, I was lucky enough to draw two, both among the best in the business. Ben Sevier said he loved it but that it could be better and gave me fourteen pages detailing how. Marc Resnick chimed in with stellar suggestions that took it to the next level, then shepherded the result with fierce energy, guarding and guiding the book for a year. If it were up to me, their names would be on the spine as well.

My sincerest gratitude to all the folks at St. Martin's Press, a publishing house of the first order, peopled by some of the most passionate and talented individuals I've ever met. Special thanks to Andy Martin, Matthew Shear, Sally Richardson, George Witte, Matt Baldacci, Dori Weintraub, David Rotstein, Christina Harcar, Kerry Nordling, and Lauren Manzella.

Assistant Director Patrick Camden of Chicago PD News Affairs and Commander Nick Roti of the Gang Intelligence Unit both had enormous patience for a barrage of foolish questions. A particular thank you to officers Dave Trinidad and Joe Perez, two cops who ride the front lines – and who lent me the bulletproof vest to join them. Finally, a shout-out to my friend Officer Jason Jacobsen, LAPD firearms instructor, South Central gang cop, and former Army Ranger, who gave me a mountain of material and corrected some embarrassing errors.

I'm also grateful for the expertise of Captain Robert Brechtl, an investigator with the South Bend Fire Department; Tim Cummings, a veteran with a keen eye for all things Army; and Dr. Vince Tranchida, New York City medical examiner.

When I couldn't figure out what happened next, when I had backed myself into a corner, when I was losing hope on the thing as a whole, my good friends Marc Paoletti, Michael Cook, and Joe Konrath took turns saving my butt with hours of beer and brainstorming. Thanks, boys.

I'm fortunate to have the finest, most tolerant group of early readers out there. Thanks to Jenny Carney, Tasha Alexander, Dana Kaye, and Pete Boivin for not flinging the manuscript across the room. And a special cheers to Brad Boivin, who gave me the hint about Jason's character that brought the whole thing together.

As always, my friends kept me going – yeah, y'all in Atlanta, too – and for that, I'm eternally grateful.

I owe more to my family than I will ever be able to repay. Mom, Dad, Matt: you guys are the reason.

Finally, love and thanks to my wife, g.g. I'm a novelist, but I don't have the words.

Marcus Sakey