Cherie Priest returns us to the scene of her great triumph, Boneshaker, in The Inexplicables. We're back within the walled city of Seattle where, years before, a tragic industrial accident undermined the city and released a mysterious yellow gas that is fatal and also causes the dead to resurrect as shambling, cannibalistic creatures called rotters.

Boneshaker was the foundation upon which Priest built her highly successful Clockwork Century series, an Old West interpretation of the steampunk genre in which the Civil War has dragged on for decades, encouraging a vast boom in military-grade technology. The writing in The Inexplicables may just be her best yet; unfortunately, she gives us a main character, Rector, who's whiny, abrasive, self-centered, drug-addicted and generally hard to like.

Rector, raised in an orphanage outside the walls of Seattle, suffers pangs of guilt for helping his friend Zeke find access to the inner city years before. Haunted by Zeke's ghost, Rector -- now 18 or 19 and ousted from the orphanage, from which he stole valuable supplies as a final insult -- decides to venture inside the city himself and lay the ghost to rest. Or at least find a reliable source of sap, the highly addictive and usually deadly drug derived from the city's yellow gas, which Rector deals and is himself addicted to.

Of course, Zeke ain't dead, which raises questions about that ghost. Forget about it, it won't be explained.

Much of the book centers around Rector's attempts to get used to city life, traveling over rooftops or through underground passageways, wearing a gas mask whenever exposed to the open air and trying to protect his skin from the caustic burns of the blight. There's also the matter of a sasquatch or two, called inexplicables by the locals, which might be on the loose in the city, too.

And then, competing gangsters who want a piece of the sap trade blow a hole in the wall and attempt to take over the town.

Fans of the series will welcome the return of many familiar characters from previous books, from sky captains to sheriffs, gangsters and one-armed barkeeps. Mercy Lynch, the resourceful nurse from Dreadnought, is especially nice to see, although I wish she'd had a larger role here. Zeke and his pal Houjin are major players in this adventure, and I kept wishing they'd step up and draw the focus entirely away from Rector, who improves somewhat along the way but never becomes truly likable.

Word is that this is the final installment in the series, which is a shame. It's been a great ride, but good writing fails to elevate this slow-moving book as high as its predecessors. I hope this particular bug bites Priest again, enough for her to find one more tale to tell in this amazing setting.