This is a brave and artful novel disguised to appear safe and conventional. One can read on for some time as if it were simply a “terror stalks the high seas” thriller, but one would be an uncommon fool to do so for very long.

Joseph O’Connor, an Irish critic and playwright who is also the author of several previous novels, lures us into an easy read that, before we know it, becomes a chilling indictment not of a murderer but of us. As a London publisher says midway through the book, advising a writer unsuccessfully peddling his fiction, this is “a good old thumping yarn,” the sort of thing a reader can “sink his tusks into.” But Star of the Sea is also an agonizing inquiry into the nature of abandonment and the difficulty of finding anyone who will truly care about the fate of others. How large does suffering have to loom before we take notice? O’Connor suggests that we can tolerate mountains of misery, sipping our coffee and reading our newspapers as the corpses pile up beneath the headlines.

The Star of the Sea is a leaky old tub sailing from Ireland to New York in the terrible winter of 1847, carrying in its staterooms a reluctantly intertwined collection of characters. The most noteworthy is an Irish aristocrat, David Merridith, Lord Kingscourt, whose Oxford training has shown him “how to put on like a cheerful idiot” while he’s got his “hands sliding around your neck.” Merridith and his family are being stalked by a man named Pius Mulvey, who has been charged, on pain of death, with executing the aristocrat before he reaches America. Mulvey’s orders issue from a group of Irishmen who resent Merridith’s eviction of his tenants, leaving them to starvation as he takes his bankrupt but very comfy self off to the New World.

Connected to both Merridith and Mulvey is a peasant woman, Mary Duane, who has cause to disavow the lot of them, and yet does not. In a world where abandonment seems the outcome of all human ties, Mary Duane remains true, against all reason. She alone seems poignantly but absurdly loyal. Her Cordelia-like heroism is alien to the novel’s plot and thus a moving but pointless anomaly.

Also on board is a cargo of steerage passengers, ill and starving, on their way to what they trust will be a new life, or at least a life. Their chronicler is another passenger, Grantley Dixon, an American journalist who writes for The New York Tribune, a man possessed of a self-congratulatory voice of confident compassion. He records the horrors of the Irish potato famine and its million dead - from starvation and from the callousness of Anglo-Irish landowners and English politicians. Dixon reports all this with a moral zeal that is as gratuitous as it is perceptive: “To remain silent, in fact, was to say something powerful: that it never happened: that these people did not matter.” Aware that these Irish peasants have died, as he puts it, “in the dark,” Dixon is also aware of both the sonorousness of his wordplay and the excitement it gives him to use it. Through this reporter, O’Connor shows how little speaking of such things can matter; Dixon’s talk participates in the same self-regard as Merridith’s, serving to shut out the rest of the world, especially those who might have some claim on their (and our) sympathy.

It is Dixon at his most assured who opens the novel with a chapter called “The Monster,” a drooling and wildly overwritten portrait of Pius Mulvey that allows us to believe, at least for a while, that we are in the midst of a comfortable melodrama, inhabiting a world so simple that terms like “evil” can be easily defined. But Dixon ends his slavering indictment of Mulvey with an admission that the monster is simply a useful fiction, providing “the illusion of unity” to a group only capable of binding itself together “not by what it shares but ultimately by what it fears.”

As we get to know Mulvey, we see how little it matters that he is a monster, how irrelevant. His monstrousness consists really in casual cruelties of an everyday sort. And much of his previous criminal activity is strangely admirable, stemming from highly imaginative schemes for keeping himself alive. Like the other characters, Mulvey takes us back to revisit his past; for a time, he lives with “freaks and bearded ladies” in a traveling circus and comes to respect their ability “to make a living out of perceived inadequacy.” He finds them “brave,” and we ourselves may come to see his inventive adaptability, his Dickensian bravado, in the same light. This is not a novel that encourages quick or confident judgments.

Mulvey’s most horrific violence is exercised in an escape from an unjust confinement in Newgate prison, brilliantly portrayed as a den of legal sadism. Mulvey kills a guard who is also his tormentor, a man at least as reprehensible as Mulvey, even at his most gruesome: “Mulvey began beating him hard with the rock, pummeling him in the face until his cheekbones collapsed and his left eye burst open like a shattered egg. He tried to call out and Mulvey stepped on his neck, grinding his foot as though crushing a snake. ... He sank to his hunkers, murmured an Act of Contrition in his dying rapist’s ear and bashed in what was left of his face with the rock.”

This is horrible, and Mulvey’s actions get worse. But it is a mug’s game to try to distinguish degrees of mercilessness in this novel.

The one seasoned optimist is the ship’s captain, whose log of the voyage is dutifully copied down by Dixon. The captain sees most clearly the suffering of his humblest passengers, and also sees most clearly that assigning causes for that suffering, speaking of its horror, analyzing it, is a way of escaping responsibility for doing anything about it. He and Mary Duane are the only ones who refuse to devote their lives to escape.

The captain looks down into steerage and confronts such wretchedness that he cannot stop himself from dreaming that in some world, somewhere, people would be bothered by it: “And it is all so bitterly unmerited. For as truly as the night comes down on every day, if the world were somehow turned downside up; if Ireland were a richer land and other nations now mighty were distressed; as certain as I know that the dawn must come, the people of Ireland would welcome the frightened stranger with that gentleness and friendship which so ennobles their character.”

But as he reveals the stories of those aboard the Star of the Sea, as he shows us Mulvey reluctantly stalking his quarry, O’Connor also makes clear how many of the Irish ruthlessly exploited the famine for their own personal gain. The captain’s dream may be noble and heartfelt, but it makes as little contact with reality as Dixon’s cocky analyses.

And, in a nasty twist, the promised land that awaits these “frightened strangers” offers yet more cruelty and death. Their ship is quarantined in New York Harbor, and many of the steerage passengers are permitted to die there of cold and starvation as New Yorkers, fearful of contagion, seek to save their own skins. City dwellers awaiting family members row out to the ship and call their names, as if doing so “was to speak the only prayer that can ever begin to matter in a world that turns its eyes from the hungry and the dying.” Saying the names is an assertion: “They were real.” They mattered.

But did they? To whom and by what reckoning? O’Connor writes well here of what George Eliot called that vision of “ordinary human life,” ordinary human suffering, that we cannot let into our hearts. “It would be like hearing the grass grow and the squirrel’s heart beat,” Eliot said, “and we should die of that roar which lies on the other side of silence. As it is, the quickest of us walk about well wadded with stupidity.”

O’Connor is not, perhaps, speaking of ordinary suffering, though the massive number of corpses makes the nightmare here seem run-of-the-mill. In any case, few modern writers have exposed with so much passion and skill the protective measures, the wadding of stupidity, that we wrap around ourselves. Neither O’Connor nor Eliot underestimates the cost of caring. It may kill us. Even so, how can we make our ignorant comfort tally with that roar on the other side of silence?