The talents for Irish atmosphere and character on display in Dunne's Goodbye to the Hill (1966) are only tapped a bit in this fast, tight, not-quite-riveting I.R.A. thriller. Someone claiming to be Colonel Valentine of Britain's ant-I.R.A. intelligence unit arranges for English bomb-expert Sonny Gunn to be sprung from prison; and then ""Colonel Valentine"" sends Sonny off to Ireland to infiltrate and spy on a commando-training brigade there. Sonny, thrilled to be out of stir, does his best--but, in virtually no time at all, his cover is blown and Sonny is executed by the Provos. The killing, however, has only just begun--because Sonny's twin brother Steve, an ex-Army trained killer (""a bloody destruction machine"") now happily employed as a gentle gameskeeper, receives a tormented posthumous letter in which Sonny names the four Provo biggies who sentenced him to death. So off goes deadly Steve to Ireland, quietly determined to assassinate those four I.R.A. chiefs (with ingenious plots and disguises). And meanwhile, the real Col. Valentine has a double mission: to try and stop Steve's murder march (it is endangering chances for an Ulster truce) and to figure who the phony Col. Valentine was--the man who planned that it all should turn out exactly the way it has, Dunne handles the Steve/Valentine alternating focus with professional ease; but neither Valentine (who has a terminally alcoholic wife and a fed-up mistress) nor Gunn (a decent fellow emotionally maimed by childhood sexual abuse) ever really grabs gut sympathy for his quest. As a result, this cleanly plotted and crisply delivered action-suspense ever so slightly misses the target--taut, literate work just a bit short on originality and emotional involvement.