As darkness falls one evening in October 1891 in Butte, Montana, Tom Rourke, an Irishman “twenty-nine years to heaven,” heads out to see what the night has to offer. Well-dressed but frayed at the edges – “in suave array and manic tatters” – Tom sips beer and slaps shots in the Pay Day, the Cesspool and the Graveyard. Drink and dope help him forget his many debts.

He rubs shoulders with – or rubs the wrong way – Danny the Dog-Boy, Jeremiah The Chin Murphy and Shovel Burgess. He makes up songs and writes letters for the lonely and illiterate in want of a bride from the East. Things take a downward turn in the wee small hours: He loses his faith in the street, has his heart broken in a brothel and considers ending it all in his rented room.

Sleepless and hopeless, he drags himself to work and meets someone who turns his life around. Kevin Barry’s new novel, “The Heart in Winter,” gets underway with an exhilarating account of a long and riotous night’s journey into day. The Irish author could have carried on in this vein, tracking his protagonist as he continues to crash and burn.

Instead, he throws Tom a lifeline in the form of love from a good woman. But that love is forbidden and so comes at a high price. What starts as a gritty depiction of one man going nowhere soon becomes a gripping tale of two lovers on the run.

“The Heart in Winter” By Kevin Barry Doubleday. 256 pages. $28 Tom’s life-altering encounter is with Polly Gillespie, who has just .