SUBTLE BLOOD presents Kim and Will in a new phase of their lives, one where Kim is no longer with the bureau and spends his days in the bookshop with Will. Their new equilibrium is disrupted when Kim's detestable brother is (rather plausibly) accused of murder. Kim has to care because if his brother dies he will stand to inherit his father's estate and title, along with the increased scrutiny that would make his life as a gay man much harder to navigate, or at least more difficult for he and Will to maintain any social fiction that they're anything but lovers. Capricorn has been dealt with, but it gradually becomes apparent that some form of Zodiac is still in play. The organization is full of people who had their own reasons for joining and perpetuating various kinds of harm in exchange for money and power, and those reasons didn't go away just because their leader met his end. 

Finishing out the trilogy, SUBTLE BLOOD wraps up all the dangling narrative threads that I could think of in a way which makes the characters’ lives feel ongoing, while still addressing what’s happened in this particular segment of it. The first two books leaned rather heavily on the idea that Kim is a particular kind of scoundrel who needed to work on some things before he could be in a relationship based on truth rather than various types of lies. SUBTLE BLOOD at long last addresses some of the ways that Will was changed by the Great War, asking him to figure out which of those coping mechanisms were still helpful, and which might better be given new shapes. This does a lot to make it clear that it's not a dynamic where Will is perfect and Kim needed to change. They both have things to work on, it's just that Will's particular coping mechanisms were more socially acceptable or less obvious for a while. 

It would definitely not make sense to start here without reading the other entries. Not only is this the final book of the trilogy but it’s one which addresses a lot of personal growth. Some form of confrontation with Kim’s awful father and brother have been a long time coming, and here it is. SUBLTLE BLOOD opens with Kim‘s brother accused of murder and acting the entitled and affronted noble, as if that’ll get him out of it without consequence, Kim is no longer with the bureau, but he hasn’t lost the skills he gained their, nor whatever appetite for skullduggery drew him to it in the first place. I like this as an ending to the series, and I've enjoyed getting to know Will and Kim.