The Hell Screen by I J Parker

The second Sugawara Akitada novel, but set later in his career than the fourth.

This was not as compelling as the other two I have read, with one of the mysteries telegraphed so much that the only surprise was 'when will the characters work it out?'

On the other hand, the characters and historical detail are just as good as the other novels. Although not quite as good, it's still very good.