Karen Chisholm

The 3rd Cormoran Strike novel, and the 2nd that I've read in the last week :)

From the Blurb:

When a mysterious package is delivered to Robin Ellacott, she is horrified to discover that it contains a woman's severed leg.

Her boss, private detective Cormoran Strike, is less surprised but no less alarmed. There are four people from his past who he thinks could be responsible--and Strike knows that any one of them is capable of sustained and unspeakable brutality.