International blackmailers are scheming to rupture relations between Britain and the United States--but Bill Loftus of Department Z is hot on their trail . . .   With America's most powerful industrialists, British peers of the realm, and agents of unknown power all entangled in a conspiracy, international safety is at risk. But unraveling this global plot quickly becomes personal for Bill Loftus when the blackmailers murder someone dear to him.   As things heat up and the stakes rise, Loftus must use all his professional cool to carry on with the investigation. The only question is whether the grief-stricken agent will be able to stop the criminals before the NATO alliance collapses . . .