Trinity

Set against the centuries-long conflict between the Irish Catholic population and their British Protestant rulers, the novel spans from the 1840s Great Famine to the eve of the 1916 Easter Rising. Narrated primarily by Seamus O'Neill, a Catholic boy from the hill village of Ballyutogue on the Inishowen Peninsula in County Donegal, the story follows multiple generations bound by land, religion, and colonial power.

The novel opens in May 1885 with the death of Kilty Larkin, a legendary Fenian (Irish republican revolutionary) and famine survivor who is the grandfather of Seamus's closest friend, Conor Larkin. Kilty's passing ignites a conflict between Conor's father, Tomas, the village's uncrowned chieftain, and Father Lynch, the autocratic parish priest. Tomas believes the priests manipulated the dying, excommunicated Kilty into accepting absolution, but Conor reveals that his grandfather chose freely. Tomas refuses to enter the church for the funeral mass, and Father Lynch condemns him to eternal damnation.

During the wake, the aged shanachie (storyteller) Daddo Friel narrates the Larkin family history. He recounts how Conor's great-grandfather Ronan Larkin led the Catholic Defenders, a militant agrarian group, in County Armagh, was flogged nearly to death after the 1798 United Irishmen Rising, and fled to Inishowen. He also relates the Great Famine: how the estate agent MacAdam Rankin used the potato blight to carry out mass evictions, how Kilty's brother Aidan was killed resisting, and how young Tomas watched his siblings and mother die. These experiences forged Tomas into a practical farmer who distrusts both republican fantasies and clerical authority.

The novel also introduces the Protestant establishment. Kevin O'Garvey, a Catholic solicitor and leader of the Land League, a tenant-rights movement, challenges the Unionist member of Parliament for East Donegal. Sir Frederick Weed, the industrial titan of Belfast whose Weed Ship & Iron Works employs thousands of predominantly Protestant workers, courts an alliance with Roger Hubble, heir to the Earl of Foyle, who is modernizing the Hubble earldom by converting tenant farmland into ranches and factories. Weed's daughter Caroline marries Roger, merging two of Ulster's most powerful families.

At the Apprentice Boys celebrations in Derry, annual Protestant commemorations of the city's siege, the Reverend Oliver Cromwell MacIvor delivers an inflammatory sermon. Conor and Seamus, who have sneaked into the cathedral, are discovered and chased through the streets. MacIvor's incitement sparks a riot in which Catholic homes are burned and lives lost. Afterward, Charles Stewart Parnell, the leader of the Irish parliamentary nationalist movement, speaks to Conor about Irish identity and gives him Thomas Paine's The Rights of Man. Kevin O'Garvey wins his seat in the 1885 landslide, but the triumph proves hollow: Lord Randolph Churchill tours Ulster stoking anti-Catholic agitation, the Home Rule Bill is defeated, and Parnell is later destroyed by the exposure of his affair with Kitty O'Shea, dying in 1891.

Through adolescence, Conor apprentices at a blacksmith forge and reveals extraordinary talent for ironwork, while Seamus studies under the Scottish teacher Andrew Ingram. During a summer at a booley house, a seasonal mountain hut used for grazing, they devour smuggled books on revolutionary Irish history. Tomas offers Conor the farm, but Conor wants to be an ironmaster. This rejection festers until the family ruptures: Liam, the younger brother who loves the land, announces plans to emigrate because Tomas will not give him the farm. Conor confronts Tomas, declaring he will never take the land, and leaves Ballyutogue without looking back.

In Derry, Conor discovers the sectarian economic system that denies Catholics all but menial work. He establishes a forge in the Bogside with a loan from the Bogside Association, a local Catholic organization, and builds a thriving business. When his forge wins a contract breaking the Protestant monopoly, it is burned in retaliatory arson. Kevin O'Garvey, who has secretly dealt with Brigadier Maxwell Swan, Sir Frederick's intelligence chief, to suppress a parliamentary investigation of the Witherspoon & McNab shirt factory in exchange for Bogside Association funding, forces the forge's restoration by threatening exposure. The factory subsequently catches fire, killing over a hundred workers. Kevin disappears and is never seen again. Conor leaves Ireland in despair.

Meanwhile, Seamus has become a journalist in Dublin. Long Dan Sweeney, an old Fenian who spent decades in British prisons, reassembles the Irish Republican Brotherhood (IRB), a secret oath-bound revolutionary organization. Conor returns, joins the Brotherhood, and is assigned to Belfast, where he secures a position at the Weed Ship & Iron Works through the intervention of Caroline Hubble and her son Jeremy. Playing on the East Belfast Boilermakers rugby team provides cover while Conor devises a scheme to smuggle guns from England using Weed's private train. The operation succeeds on multiple trips. Conor falls in love with Shelley MacLeod, the independent Protestant sister of his rugby teammate, but their relationship forces a crisis between personal desire and revolutionary commitment. Shelley recognizes that fleeing Ireland will destroy Conor, and she departs, telling him she will not let him wither in exile.

The gunrunning ends in catastrophe at Sixmilecross when Doxie O'Brien, the Boilermakers' Catholic assistant coach, betrays the scheme to Sir Frederick. British soldiers ambush the final weapons drop; Conor is shot twice but escapes. He is eventually captured and, at a secret tribunal, delivers a speech arguing that Britain's presence in Ireland is illegal. He is sentenced to 50 years. Shelley is murdered by Protestant women from MacIvor's church. Conor, in solitary confinement, retreats into catatonic silence before releasing his grief in 30 consecutive hours of screaming. His brother Dary, now an ordained priest, engineers Conor's escape from prison.

At a remote Connemara estate, Atty Fitzpatrick, a widowed republican and Brotherhood Council member, nurses Conor back from the edge of death. They become lovers. Conor takes command of Brotherhood training but refuses the supreme command, telling Atty the Irish cannot win militarily and can only achieve glorious defeats that may stir the people's dormant spirit.

As the Home Rule crisis intensifies from 1910 to 1914, Sir Edward Carson, the Unionist leader, raises the Ulster Volunteer Force (UVF), a hundred-thousand-strong private army. Christopher Hubble, Roger and Caroline's son and an army major, orchestrates a mutiny of officers who refuse orders to move against Ulster. Roger's ruthless destruction of his elder son Jeremy's love affair with a young Catholic woman reveals the irreparable fracture within the Hubble family.

For the climactic mission, Conor plans to destroy Lettershanbo Castle, the UVF's primary arms depot, using a secret tunnel from a sea cave. A team of 22 crosses the strait from Inishowen in curraghs, small traditional Irish boats, during a storm; two boats are lost. The survivors plant dynamite in the castle's boiler room. When a guard discovers the intrusion, Seamus holds him off with gunfire while Conor, at the detonator, faces the choice between waiting for his friend and blowing the castle. Conor triggers the explosion, killing Seamus and igniting three hundred tons of stored explosives.

Conor and the dying Dan Sweeney make a last stand at a Martello tower, a small coastal defense fort, covering the survivors' retreat until their ammunition runs out. Dan is found dead; Conor is found mortally wounded, and a British officer shoots him. Their bodies lie in state in Dublin's City Hall, and a funeral oration in Irish galvanizes the nation. Conor is buried beside Tomas in Ballyutogue. Ten months later, the Easter Rising of 1916 takes place. The British execute its leaders, and a republic eventually comes to pass, yet the novel's final words insist that "in Ireland there is no future, only the past happening over and over."