Luke’s (Lucifer’s) Sin by Lisa Renee Jones

His mother called him Lucas. His brothers in the military and Walker Security call him Lucifer for his wild side. She called him the man she loved, she called him Luke. But then he proved he really is worthy of his nickname. Or so she thought. Nothing is as it seemed back then. A man with a past. The only woman he has ever loved. Someone wants her dead. That someone is about to find out that yes, he is Lucifer when you dare to threaten his woman. Even if she doesn't call herself that now. He does. But all he ever really wanted to be was Luke—the man worthy of her love. Book one in the Walker Security: Luke (Lucifer) Trilogy.