ぬれぎぬ

Two years ago there was a series of killings with rape going on for two months, but police never found the culprit. Main character witnessed at that time how a middle-aged man was violating his acquaintance, but was paralyzed with fear and could not do anything and that woman was found dead.
Nowadays the killings have started again. Hero wants to protect everyone he knows, but will he be able to do that?