Red Sky At Night

Description for RED SKY AT NIGHT by James W Hall:

It happens in an instant. A man's life is ripped form the safe harbor he's almost found, hurtled back into the violence he has been running from for years. The man's name is Thorn. While investigating the bizarre slaughter of eleven trained dolphins, Thorn is viciously attacked. Crippled by pain, he is bitter enough to drive his lover away, desperate enough to seek medical miracles at an experimental clinic. There, his old friend, now a doctor, is on the brink of an awesome discovery: a cure for human pain.

Within hours of entering the Key West clinic, Thorn can sense danger. Patients are isolated. Experiments are spinning wildly out of control. Suddenly Thorn knows just how fare his friend will go to find a cure. Now, as a storm of greed and human suffering gathers around him, Thorn is scratching and clawing his way back to a life he almost had, back to the woman he almost married, and to the darkest truth of all: There is some pain that only killing can end.

this is #6 in Thorn Series.