Devil Dog: Out of the Dark3 books in series
Devil Dog Publisher's Summary
Dick, AKA Devil Dog's world changes drastically when the EMP takes out the power grid. The loss of electricity brings out the darker side of human nature across the city. A homeless Marine veteran living in the abandoned tunnels beneath Chicago, he's far better prepared than most people. Good folk have survived, but they are often outnumbered and outgunned. Only the tunnels provide the safety he needs.
Devil Dog becomes the reluctant savior of women and children from the worst of the gangs that now rule topside. Doing the right thing makes him new enemies, driving him ever deeper into the tunnels that keep his charges safe - until he runs across a young woman who might be his daughter.