Seeking a dark 1980s (?) novel with an antagonist named Arlis?

I forgot the name and the author. The book was very disturbing and dark, and the subject matter not normally something I would have read, but it has stuck in my mind for years and I would like to at least find it to determine if I do want to read it again.

It wasn't horror, more like a crime thriller or crime drama. The basic plot is this sick pedo named Arlis kidnapped an 11-year-old boy for his jollies. The only other thing I remember from the book is that he took the boy into a motel under the guise that he was his "son," and I believe it was at this or a similar motel that he was eventually caught. The boy survived the ordeal but was traumatized and twisted, and he had developed a kind of "Stockholm syndrome" attachment to Arlis.

I believe the novel was from around the late 1970s to early or mid 1980s, because I was reading a 1983 novel called Worst Enemies around the same time. (Worst Enemies was by Jack Scaparro, but I'm quite certain he wasn't the author of the book I'm seeking.)