Readers of Jeff VanderMeer's fantasy stories about the city of Ambergris ("City of Saints & Madmen," "Shriek: An Afterword") will hardly recognize the old place in this noir sequel. The "gray caps" -- mushroom-like aliens driven underground centuries ago by the city's human founders -- have risen and seized control. Using slave labor, they are building two gigantic towers that will create a "door" in time and space, so that they can either return to their home planet or bring in reinforcements.
His new novel, "Finch," opens with a human detective, John Finch, being tortured by someone who demands information about the "rebels" -- the dispersed remnants of the armies of Ambergris' two great trading houses, Hoegbotton and Frankwrithe & Lewden, whose ill-fated invasion of a nearby desert empire six years ago gave the gray caps their chance. In particular, Finch's interrogator wants to know if he has met the rebel leader, the Lady in Blue, whose charismatic radio broadcasts have almost died out.
Gradually, we understand that Finch's ordeal, to which we return every few chapters, is at the end of the story -- all the rest is flashback. "I am not a detective," he keeps insisting. In fact, Finch isn't his real name. His father was a Hoegbotton operative, an architect of the desert war and perhaps a multiple traitor. To hide this background, which could easily get him killed, Finch works in a police station, investigating routine crimes, as if humans were still in charge -- though he has to report to the gray caps, which makes him, in effect, a collaborator.
"Everyone's a collaborator. Everyone's a rebel" proclaims graffiti in the fear-ridden, half-flooded city. Finch can't trust the gray caps or their henchmen, the Partials -- hybridized humans who have traded their souls for an acute, photographic vision. And they, of course, don't trust Finch. His girlfriend, Sintra, keeps herself at a disquieting remove. Rathven, a female librarian who helps Finch research his cases, must be a spy for somebody. But whom? Even Finch's longtime police partner, Wyte, has become unreliable: Spores from the gray caps' fungal weapons have colonized his body, which is falling apart as plant matter replaces flesh.
It's a familiar, hard-boiled scenario, despite all the fantasy. Like China Mieville ("Perdido Street Station," "The City & the City"), VanderMeer creates a dense and persuasive imaginary universe, in which the things that also belong in our universe -- tanks, whiskey, revolvers, the paranoid feel of a Raymond Chandler or James Ellroy whodunit -- strike us as oddly comforting. Finch, ordered to investigate the double murder of a gray cap and a human, is in big trouble, but it's trouble we know.
The gray cap has been mysteriously sliced in two. And the human, Rathven discovers by checking old records, is historian Duncan Shriek (co-narrator of "Shriek: An Afterword"), who should have been dead already for 100 years. Finch finds a solitary clue by eating the "memory bulbs" that, in Ambergris, sprout from people's heads after death. Shriek's memories include a vision of a desert fortress and the name of Ethan Bliss, a spymaster who once worked with Finch's father (or against him, or both).
What follows -- though tangled in back story, just as Ambergris is festooned with malignant fungi -- is pure action, which VanderMeer, a talented stylist, renders in bursts of staccato sentence fragments. (Like this. And this.) For a few frenetic days, Finch chases Bliss, who leads him to the thuggish pirate leader Stark, who leads him, indirectly, to the Blue Lady, who tells him that Shriek's corpse just might be the key to saving the world. Finch suffers extravagantly -- not just at the hands of his torturer and other bad guys, but because he's still capable of love as well as violence. Down these alien streets, as Chandler might say, goes a man who is not himself alien, and we're willing to follow him almost anywhere.
Harris is a critic and the author of the novel "The Chieu Hoi Saloon."