Under The Marshal's Watch by Jaycee Bullard

With innocent lives at stake, he’ll do anything to protect them.

US Marshal Jimmy Flynn’s mission to guard his witnesses in a safehouse should be straightforward — until hitmen breach the location with intent to kill Isobel Carrolls and kidnap her son. Now it’s up to Jimmy to keep Isobel and her child safe as they travel across state lines so she can testify against her criminal ex-husband. But with relentless gunmen anticipating their every move, his mission is a race against time. Can Jimmy keep them alive long enough to expose the truth...or will the dangerous pursuit cost them everything?