A review by vesper1931
Untrue till Death by Graham Brack

4.0

1674 Leiden, Netherlands. Mercurius is sent by William of Orange to investigate his agent at Utrecht, who he believes is too old for the assignment and wishes Mercurius to help find a replacement, when a colleague at the University of Leiden is killed. But is Mercurius in danger of forfeiting his life.
An entertaining and well-written historical mystery.