Flossie Rubrick is a formidable New Zealand Member of Parliament and lives on a remote sheep farm with members of her family, one of whom may be spying for her country's enemies.
One evening during the summer of 1942 Flossie disappears after she goes to her husband's shed to rehearse a patriotic speech. Three weeks later she turns up dead at an auction, inside one of her husband's bales of wool.
Roderick Alleyn, working for military intelligence during World War II, visits New Zealand in the Autumn of 1943 to investigate possible Nazi spying and has to find out retrospectively what happened to Flossie and which of her extended family is both murderer and maybe enemy agent.
The plot structure is unusual with the investigation occuring 15 months after the murder and enables Marsh to develop the character of the victim, Flossie Rubrick, in unusual detail.
The New Zealand location, probably near Mount Cook, is well depicted in a story which is similar to the previous novel in the series, Colour Scheme, with Alleyn's counterespionage work providing a change from his normal police duties.
The unusual plot structure, setting and storytelling in this book make for a noteworthy example of Marsh's writing and I think this is well worth reading.