Heartbreak by John Righten

1990. Lenka Brett, a smart but unworldly, young Irish teacher, volunteers to deliver medical aid to Romanian orphanages after horrifying plight of children abandoned there. An English naval officer, Captain Simon Syrianus, volunteers to be her co-driver. Together, they join a convoy of humanitarian aid drivers known as the Rogues, men and women who are the last hope for those trapped in areas where official charities cannot enter.
Lenka falls in love, but when the Rogues become the target of mercenaries, tragedy follows and she discovers her lover is not who he appeared to be.