Murder By Day by Rebekah Dodson

It’s been a little over a year since Maggie and Daniel “Jesse” Cabot were stranded on the California Express, a terrorizing three days that changed their lives forever. Now in a troubled marriage with a 9-month-old daughter, they are ready for a long-awaited honeymoon to Hawaii – no trains involved.
But when they arrive in Portland, Jesse gets a new mission from the CIA, and their plans change for the worst. Another train ride, this time as a bodyguard for eight of the world’s most famous billionaires. Under death threats and secrecy, the trip to an environmental summit in Las Vegas is wrought with danger.
After a series of tragic events, it’s up to Maggie and Jesse to discover a murderer aboard the stranded California Express, and rekindle the romance they once knew, before it’s too late.