The popularity of cosy crime speaks to our fatigue (especially this year) and our nostalgia (not satiated by The Crown) rather than to more troubling attributes like class envy or unthinking Anglophilia. In summer, when we spend too long peering at too much of our bodies, we are supposed to seek out a little suspense, a few exotic settings and - best of all - the promise of a tidy, happy ending.

Those assumptions do not take account of the fact that the classic Christmas story features a selfish misanthrope, a tragically crippled child and a ghost rattling his chains. Nor do the publishers of cosy crime acknowledge that some readers might relish a challenge over summer, and therefore buy a brick of a book for the beach. A bookseller once recommended A Place of Greater Safety; its 872 pages of tiny print sustained me between many a surf and a beer.

At first blush, were she ever to blush, Phryne Fisher does not fit the usual mould for cosy crime. Phryne is young, although she whinges tiresomely about turning 29. She sleeps with an erudite, vigorous Chinese rather than keeping company with doddery buffers. She shoots, but not merely docile stags and feral foxes. Although she drinks tea, that tannin is leavened by lots of other fortified liquors.

Greenwood has shrewdly decided not to use first person singular narration, not to let Phryne tell her own story. That technique inserts a certain ironic distance between the reader and Phryne's appalling snobbery, her outlandish selfishness and her patronising views on the world at large. The #MeToo movement would not easily tolerate a full-frontal version of Phryne Fisher.

This 21st episode in Phryne's life locates her in familiar territory, Melbourne in the 1920s, then shifts her up into the bush, albeit a manicured, house-trained version of country life. We first encounter "impossibly elegant" Phryne risen from "wickedly crimson" sheets, wrapped in a "spotless" cotton towel, on her way to consume the contents of a "prodigiously laden" breakfast trolley. If all those adjectives and adverbs appear retro, over the top and affected, that might be precisely the impression Greenwood is intending to convey.

Phryne is summoned to Hepburn Springs near Daylesford, spots as seductively attractive in 2020 as they were during the 1920s. She is predictably investigating acts of skulduggery, prompted first by disappearances by local women. In case that narrative flags, Greenwood introduces a sub-plot, each with the requisite amounts of villainy, blundering policemen, adroit detection and derring-do. That concerns the corpse of a pregnant girl discovered in the eel-infested Yarra River.

Greenwood's command of period detail is admirable, except for her depiction of the working class. Again, we see through Phryne's privileged, myopic eyes the "Unwashed Suburbs", filled with "horny-handed" labourers who say "yous" and "yair". The public bars those toilers frequent embody "primeval squalor". Few members in that gallery of proletarian bit parts are at all convincing, however dutifully loyal and helpful they might be to their so-called social betters. That deficiency has been evident across a number of the 21 Phryne chronicles.

Greenwood is on safer ground when she focuses on Phryne, whether "a picture in shades of Picasso blues" or in any other of her lavish, lovingly described outfits. Up there in rural Victoria, Phryne survives a vegetarian dinner, a diversion to a Temperance Hotel (which nonetheless serves alcohol) and a lugubrious Highland Gathering. Crisply and briskly, if always exquisitely dressed and perfumed, Phryne cuts to the chase.

Despite a few red herrings and blind alleys, Phryne nabs the culprits. A needle fired from a blowpipe to impede a caber tosser becomes a clue. Missing dentures are mysteriously found behind a toilet bowl. One miscreant is locked up in a bottling plant while another is accosted in a darkened cinema.

None of those details will spoil the enjoyment of devoted Phryne fans. They might still revel in an untroubled world where a woman laughs "like a beakerful of Irish cream being imbibed". Those devotees will likely not complain about a surfeit of sentimentality, a few too many coincidences or endless prattling by the heroine about how smart, elegant and beautiful she is. That would be akin to whingeing about Sherlock Holmes' violin playing or Sam Spade's way with women.