Hellfire by Rickard B DeMille

US Marine Travis Deacon always loves catching some R&R. And he loves being in Wales to catch it, until his best friend, SAS Major Gareth Jones, dies in an "auto accident." When Travis asks too many questions about Gareth's death, MI5 steps in and tries to send him back to Afghanistan. Then, the international terrorist who killed his friend, tries to send Travis to hell. It gets worse when Detective Sergeant Dee Jones, Gareth's sister, arrests Travis to find out if he’s involved. Together, convinced that Gareth was murdered, Travis and Dee search for the killer. They dodge terrorist assassins and British agents in their search across Wales for the truth. Suddenly, the murder investigation becomes a frantic race to prevent a terrorist attack that could change the world.