The Silent Cry is the eighth in Anne Perry's somewhat lesser known William Monk series. It has dropped to $1.99 at Kindle US and Kobo US.
Kindle US:
https://www.amazon.com/Silent-Cry-Wi.../dp/B0042JSNY0
Kobo US:
https://store.kobobooks.com/en-us/eb...e-silent-cry-1