The Girl Next Door (Harlequin Intrigue Series #1480)

He pledged to protect his neighbor, in New York Times bestselling author Cynthia Eden's Shadow Agents: Guts and Glory miniseries 

When Gabrielle Harper's gutsy investigative reporting attracted a serial killer, her new neighbor began keeping an eye on her. But Cooper Marshall was more than his chiseled frame suggested. He was an Elite Operations Division specialist who thrived on adrenaline, who always took risks, whose every instinct was geared to protect. Even if it meant breaking cover. Gabrielle wasn't the sort to hole up in her Washington, D.C., walk-up, waiting to be the next victim. So when the time came, he'd throw her on the back of his motorcycle and ride with a vengeance to save her life. Until then, he'd watch and wait, and try not to get carried away with attraction to the girl next door….