Love Kills Twice - Fatal Fidelity, #1

She needs an assassin. They're the best in the business. Falling in love was never part of the deal. Desperate to escape her abusive husband, Justine hires a contract killer. Campbell's services come at a high price, and their dark, seductive charisma leads Justine right into their bed. Hiding an affair while Campbell designs the perfect murder has Justine walking a tightrope of stress, but each time the two of them sleep together, it's harder not to get attached.
Campbell struggles with their own traumatic past, convinced that the truth will drive Justine away. There's a faint hope that things could work, save for one problem: Justine's husband wants her dead too. Revenge is easy-heartbreak could cost both of them everything.