The Breaking Point (LIN) (Linford Mystery Library)

When the dead body of small-time racketeer Firini is fished out of the bay, there is a message scrawled on one of private investigator Mike Faraday's business cards in his pocket. Firini has been blackmailing a wealthy couple over pornographic film, but another group of people, more sinister and dangerous, are also after the same reel of celluloid. Mike sets out to find the secret behind it, and on the way stumbles across a trail of corpses who have met their ends by stabbing, acid-bath or bullets.