Helena and Daniel Fleming's 10 yo autistic son Christopher finds their neighbour's nanny hanging in the barn and it obviously wasn't suicide.
Lots of ongoing story lines wrapped up in this, the last in the series, some of them in a perfunctory way in the last few pages. I will miss Jimmy, Willow, and Sandy but I appreciate the author's point that she couldn't have kept going for much longer without Shetland having a ridiculously high murder rate.