Murder on a Midsummer Night

Blurb from the book:

Melbourne, 1929. The year starts off for glamorous private investigator Phryne Fisher with a rather trying heat wave and more mysteries than you could prod a parasol at. Simultaneously investigating the apparent suicide death of a man on St Kilda beach and trying to find a lost, illegimate child who could be heir to a wealthy old woman's fortune, Phryne needs all her wits about her, particularly when she has to tangle with a group of thoroughly unpleasant Bright Young Things.

But Phryne Fisher is a force of nature, and takes in her elegant stride what might make others quail, including terrifying s ances, ghosts, Kif smokers, the threat of human sacrifices, dubious spirit guides and maps to buried pirate treasure ...