Death Before Wicket by Kerry Greenwood

Phryne Fisher is on holiday. She means to take the train to Sydney (where the harbour bridge is being built), go to a few cricket matches, dine with the Chancellor of the university and perhaps go to the Arts Ball with that celebrated young modernist, Chas Nutall. She has the costume of a lifetime and she's not afraid to use it. When she arrives there, however, her maid Dot finds that her extremely respectable married sister Joan has vanished, leaving her small children to the neglectful care of a resentful husband.