Reliable horror/suspense writer Campbell Black (The Wanting, Letters from the Dead, Asterick Destiny)--who also writes psychothrillers under the Thomas Altman byline--here adopts a second pen name for what the publisher touts as his ""breakthrough book."" But the new name and the $150,000 pre-publication campaign can't mask what's essentially a modest and fitfully satisfying thriller, albeit puffed into 495 pages, about an IRA assassin at large in the US. A solid premise underlies the action here: a fortune in US funds destined for the IRA is hijacked, and Jig, the IRA's top assassin, flies to America to ferret out the traitor from among the four men responsible for the shipment. Black draws Jig in bold strokes--he's young, canny, headstrong--but neither he nor his nemesis, British counterterrorist Frank Pagan, who pursues Jig to America, rises above type. Familiar too are the four pro-IRA Americans: Kevin Dawson, a Bobby Kennedy clone; Jock Mulhaney, who's Jimmy Hoffa with an Irish heritage; a weaselly Wall Streeter; and Harry Cairney, a rich retired US Senator. As Jig chases the four--and Pagan chases Jig--in a series of cat-and-mouse stalks, bloody confrontations, and hairbreadth escapes, Black sets up two intriguing subplots, sadly slowed by excess chat about the pros and cons of a divided Ireland. First, Cairney's wastrel son Patrick returns to the family manse, where sexual sparks fly between him and Cairney's sultry wife, Celestine--the only magnetic character in this novel. Second, a band of militant Protestant IRA-ers wreak terrorist havoc in the Northeast, blaming the destruction on Jig and the IRA. Two big but soggy plot twists bubble up--one right out of The Marathon Man, the other telegraphed into predictability--and a wholly unbelievable partnering of Jig and Pagan to stop the maniacal Protestants caps things off. Black flattens any moral tenor with his black-and-white characters (are all Protestants fanatics?) and shows little originality throughout. For all that, however, this potboiling thriller offers a modicum of tense moments, and enough verve to please undemanding readers.