Rules in Rescue by Nichole Severn

She walked away from him once. Now he’s her only hope.

Blackhawk Security weapons expert Anthony Harris has trained for any contingency...except the return of his ex-fiancee. Glennon Chase walked out on the former ranger five years ago, and now the CID special agent needs Anthony's help with a deadly investigation into her partner's disappearance. Dodging bullets he can handle, but pairing up with his ex is flat-out dangerous. Especially when Anthony discovers that the secret Glennon is keeping could get them both killed.