I had told Holmes that I wanted Margery Childe to be someone who talked with God, someone actually doing what I and countless others had spent lifetimes scrutinising, and at that moment at any rate I was convinced that this was what I was witnessing. It was galvanic. Electrifying. I wanted to take notes. Yet it was also troubling, to see before me living evidence that the limpid stream I studied could become this crashing, unruly, primal force. (p. 111)
Following a pointed and opaque argument with her mentor (did he really work out her motive for paying a visit before she'd said a word?) Mary Russell takes to the streets of London and bumps into an old friend, who introduces her to Margery Childe, charismatic leader of the New Temple of God. The movement, rooted in suffragism and feminism, offers Mary (who's graduated with a degree in theology and chemistry, and has shed her aunt and inherited her fortune) a fascinating new angle on religion: moreover, Margery Childe seems truly touched by the divine.
A series of inexplicable deaths amongst wealthy young women connected to the Temple demands the investigative skills of the Russell and Holmes partnership (thus allowing them to repair their friendship): but Mary finds herself involved more deeply than she'd intended, and an unpleasant aspect of her past comes back to haunt her.
There's one exchange, in the last ten pages, that jarred me and seemed out of character ("I've wanted to do that since ...") but overall: yes, this is Mary Russell growing up, true to herself; this is Holmes, standing back (he's absent for quite a bit of the book) and observing, often all too acutely, as Mary exercises her independence and her intellect; and A Monstrous Regiment of Women also provides a fascinating mystery and an intriguing setting.