Our heroine, the one who sometimes sings Helen Reddy when “A Spoonful of Sugar” won’t do, is a 20-something nurse named Harper Grayson. Harper lives in New England, where people are terrified of death by Draco incendia trychophyton, which is known as Dragonscale for short. Harper is compassionate enough to treat infected patients, and one of her first is a mysterious Fireman who shows a telltale sign of illness: He gives off smoke. But the Fireman brings a boy for Harper to save. She then spends a tender night of lovemaking with her husband, Jakob, who turns into a raging beast when he decides Harper has infected both of them. A major plot point is born.

Image Joe Hill Credit... Shane Leonard

A baby is conceived, too. And Harper spends the rest of the book determined to survive for that baby’s sake. But because the gold-and-black markings make it hard for the infected to hide, there are colonies of secret camps. And the book soon loses its global scale as it zeros in on one refugee zone.

Mr. Hill stays so busy examining the ways different people react to mortal danger that Satan himself gets only a walk-on. (“The devil’s tail — a slender 12-foot whip braided from fire — lashed behind him.”) A cameo!

And the community’s residents aren’t as interesting as the wild array of heroes and villains stalking “NOS4A2,” a book whose heroine and villain were indelible. Harper is a perfectly nice mother-to-be, the Fireman has done an amazing job of harnessing the power of flame, and each subplot has enough baggage to fill a 16-wheeler. But there’s a rambling quality to “The Fireman” that was absent in Mr. Hill’s other, leaner books and really resembles that of … O.K., go look up his old man.

The refuge into which Harper and the Fireman stumble seems to want to be all things to all people. At least it wants to be a microcosmic survey of human behavior. There are touchy-feely times, like when the group seems to want to buy the world a Coke: It turns out that singing and harmony can turn Dragonscale into a radiant, empowering thing. And there are times when the place feels more like the setting for a Salem witch trial. It is also problematically populated with characters who might as well have walked out of the children’s stories that Harper likes so much. The chief female villain has all the complexity of a Disney witch, although latter-day Disney witches have had better dialogue.