Aquaphobia

Peyton Hadaway, over an unforgettable, horrific incident that occurred during his childhood, suffers from Aquaphobia--an irrational fear of water. In his thirties, he does his best to keep that unknown from those that aren't already aware of it.
But someone is targeting and assaulting him and those he's close to. Eventually, Hadaway realizes they discerned of his dark secret.
Hadaway's cousin, Private Investigator, Brock Xander soon learns of this. Although he's engaged in searching for a woman that he used to know, it won't stop him from helping his relative find the culprit, while trying to save his cousin's life. The antagonist uses sharp weapons to pierce his victims flesh, like in Matt Goldman's Broken Ice.
The detective is hired to find someone he has a past with, as in Girl Jacked by Christopher Greyson.
Many of characters suffer from abnormal phobias, like in Jonathan Nasaw's Fear Itself.
Wounded people are held captive by unstable persons like in Misery by Stephen King.