Relentlessly savage days and nights in Ireland, by this British author who matches MacLean's classic Navarone gun for gut. Simon Vaughan is sprung from a Greek prison to spy for Britain in I.R.A.-land. Working through old friend Meyer, the arms runner, Vaughan teams up in Belfast with wild Irish-American Norah and her young idealist bodyguard -- and is soon on his way to spotting Norah's uncle, ""The Small Man,"" an old revolutionist, and some purloined swag. But the trio run up against the murderous Sons of Erin, out for apolitical gain, and there are brawls, chases, and split second shifts. Tough as nails -- for the coffins of those lucky stiffs not blown to smithereens.