Career of Evil (Cormoran Strike Series #3)

"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"--