Playwright Brendan Behan used to joke that the first item on the agenda of any new Irish political party was "the split." This old quip comes to mind when considering "The Dead Republic," the final installment of Roddy Doyle's modern Irish history trilogy, "The Last Round-Up": The perils of a division become one of the novel's main concerns, but the book itself can't quite avoid a split.

"A Star Called Henry," the first volume of the trilogy, exuberantly chronicled the years in which Henry Smart was "the young, hungry king of Dublin's corners" and played an instrumental role in the bloody struggle for Irish independence. The second volume, "Oh, Play That Thing," saw Henry hanging out in Depression-era America with the likes of Louis Armstrong and losing a leg to the wheels of a boxcar. In "The Dead Republic," an aging, sometimes amnesiac Henry is back in the old country.

It's the early 1950s, and the Irish Republic is a stagnant, incomplete version of the country Henry fought for in the War of Independence. To add insult to injury, the movie he's come home to make with his Hollywood buddy John Ford is turning out to be not, as promised, his gritty life story, but "The Quiet Man," that long, Technicolor commercial for the Irish tourism industry.

Henry quits the set, and settles, after a three-decade absence, in his hometown of Dublin. Reincarnated as "Hoppy Henry," the caretaker of a boys' school, he enjoys -- and the reader enjoys -- his role as unofficial policeman, protecting the students from the crueler teachers. The legend that has grown up around him as a 1916 veteran is enough to keep most of them in line.

But that legend also plunges Henry into turbulent waters when the new "troubles" break out in Northern Ireland in the late 1960s. Henry Smart is a relic of the True Cause, and everybody wants a piece of him. This becomes especially true as something approximating the peace process begins to emerge from the political and physical wreckage; "the split between the gun and the vote" has begun.

However, this second half of the novel may well leave readers feeling dissatisfied. American readers, for example, unless they have an advanced knowledge of modern Irish politics, may be puzzled by allusions to the Blueshirts, the Heavy Gang and Ernie O'Malley. Henry and other superannuated characters remain, necessarily, on the dramatic margins of the northern tragedy, and can't really do it justice.

"Do rebels never retire?" John Ford asks Henry at one point. In Henry's case, the answer is obviously no, but perhaps Doyle should have retired him. Though still capable of bursts of flinty lyricism and ornery action, Henry does not feel like the right man for this job. An entire Henry Smart novel set in the 1950s, or a novel about the immediate Irish past using a different protagonist, would have been more satisfactory than this bifurcated book.

Robert Cremins, the author of "A Sort of Homecoming," teaches in the Honors College at the University of Houston.