The story opens with Patricia Teeling at a crossroads in her life. She has just finished off an agricultural degree, which her very simpatico Uncle Lar has done most of the funding for. Lar of course wants her to take over his very shipshape farm, but Patricia wants to try city life and sow some wild oats before she settles down, almost certainly for life. So she quickly finds a teaching job in Dublin, leaving the Irish midlands behind.
And there her troubles begin.
I have to say that I read this book almost completely wrong. I took it to be a rather convincing novel of a young woman's quest for her own authentic path, which includes finding a vocation and also a mate. The fact that all the men in her life are either very limited or very dicey--except for Uncle Lar, of course--and that having experienced the city she is no longer a country girl and still not yet an urban one--makes this path particularly difficult.
Actually, though, this is a crime novel. Though no one in the book seems particularly avid to solve the crime, this is still the case, and I don't think it's much of a spoiler to say that McGinley never loses sight of the fact, even if we do. I see in the Wikipedia article that he is an admirer of Flann O'Brien, and this I think explains a lot about his approach. The same article links to a New York Times book review of the book when it came out, and although I think it's the kind of review that gives too much away, it's definitely worth reading afterwards.
And it also makes the book worth reading again after you come to the end.