It may take a few chapters beforeDonna Leon’s avid readers get over their disappointment in her latest mystery. All looks molto bene at first: Venetian setting? Check. Insider descriptions of Italian food and architecture? Check. Corrupt officials and brutal criminal bottom-feeders? Check, check.

Throughout 21 novels, Leon’s Commissario Guido Brunetti has investigated . . . Holy Cannoli, there’s no Commissario Brunetti in this story! A Donna Leon mystery without Brunetti, at first, feels empty, as though a mischievous god had pulled the plug on the canals.

“The Jewels of Paradise” is Leon’s first stand-alone mystery, and, while it is undeniably strange to be wandering through Venice without the protection of Brunetti’s solid presence, the young heroine of this novel is so winning that readers should find themselves forgiving the commissario his absence. Native Venetian Caterina Pellegrini holds a recently minted PhD in music, with a specialization in baroque opera. Jobs are scarce: As a cynic might say, that PhD and two Euros would get Caterina a cup of gelato. That’s why, when the novel opens, she has exiled herself to the damp, chill clime of Birmingham, England, where she’s slaving away as a university lecturer.

When a drunken colleague mentions an opening for a music researcher at a foundation in Venice, Caterina races to apply and lands the job. But it’s a strange setup. The foundation occupies a two-story apartment in Venice, and only one other employee works there (erratically). Caterina learns that her assignment is to excavate two recently discovered antique chests containing letters and manuscripts belonging to a 17th- and early 18th-century composer, priest and Vatican diplomat, Agostino Steffani. Two rival cousins, claiming to be Steffani’s descendants, are contesting ownership of the chests, and to settle the legal dispute, Caterina has been hired to pore through the documents to find any mention of specific bequests and determine the value of any music manuscripts that might come to light. On her first day on the job, however, she also learns that the cousins are interested in finding something more lucrative than moldering opera scores: There are rumors of a great treasure that Steffani amassed throughout his distinguished diplomatic career.

Even Caterina has to laugh at the hokiness of this case: “She had been hired for a bit part in a bad nineteenth-century melodrama: The Rediscovered Trunks? The Rival Cousins?” Leon, however, has never allowed the fairy-tale beauty of her novels’ Venetian setting to render them simply quaint. Caterina is tart and independent. When a hulking stranger follows her from work one evening to her parents’ apartment, she wills herself not to panic and even attempts to confront him. As she begins to uncover the more disturbing private history of Steffani’s life — and the more twisted motives of her employers — she receives an advanced education in depravity and greed.

“The Jewels of Paradise” by Donna Leon (Atlantic Monthly)

Caterina’s scholarly idealism is not the only thing that takes a beating in “The Jewels of Paradise.” Venice, itself, seems weary, shopworn. In a conversation with a fellow Venetian, Caterina remarks on the dismal demographics of the great city:

“ I saw in the paper this morning that there are now fewer than fifty-nine thousand of us.”

Ezio shrugged. “I don’t see what we can do. Old people die. Young people get jobs in other places. There’s no work here.” Then, tilting his glass in her direction, he said, “You’re the lucky exception. You got called home to take a job.”

It remains to be seen how “lucky” Caterina is: Not only is that research job taking a toll on her nerves, but it’s also eroding what little sliver of faith she had retained from her childhood. Throughout this novel, the terra-firma certainties that once grounded Caterina’s life become as unstable as the marshy islands of Venice itself.

“The Jewels of Paradise” is as much a tale about a young woman wising up and learning to fight more effectively for her own happiness as it is a mystery — though the centuries-old secrets that those chests contain are also pretty compelling. Commissario Brunetti is allowed to take a vacation once in a while, but only if his replacements are as wry and erudite as Caterina.

Corrigan, who teaches literature at Georgetown University, is the book critic for the NPR program “Fresh Air.”