The Invisible Man from Salem. A Leo Junker case

When a young woman is shot dead in his apartment block, disgraced former police officer Leo Junker is one of the first on the scene. Examining the dead body, he notices that the woman is clasping a cheap necklace - a necklace he instantly recognises.
Despite being warned off the case, Leo sets out on a rogue investigation to catch the killer, uncovering a series of frightening connections between the murder and his own troubled