The book, as you might guess, is somewhat different from the movie. In the movie Lancaster's character, Jim Slade, is a nightwatchman at a college. See Tuesday's post for more details. In the novel, the character's name is Morgan Butler, and he's a part-time constable and a full-time farmer. He's also a former private-investigator for a big firm. P. I. work is now his avocation, as he calls it, and he takes on high-paying, dangerous jobs to support his farming.
As in the film, there's a murder on a college campus, and Butler investigates. The murdered girl's father, a senator in the movie, is a business tycoon in the book. He wants the crime solved, and he hires Butler to investigate privately after the local sheriff closes the books on the crime, convinced that he has the killer safely locked in jail. The book's plot is quite convoluted, and it's a bit reminiscent of something Ross Macdonald might do. I remember being surprised at the outcome when I read the book 40 years ago, but not this time. Maybe I remembered it, since I did remember quite a bit of the plot, more than I thought I would. I'm not sure how a reader today would react to the story and the style, but I enjoyed reading this one again.
William Dale Smith wrote a number of books as David Anthony, and I've read three or four of them. I liked them all, but Anthony seems entirely forgotten now. I checked the Thrilling Detective website, and Anthony's not mentioned there, though Butler is clearly operating as a private-eye in this novel. Anthony's other series character is Stan Bass, and I liked Stud Game, one of the novels he appears in. He's a p.i. who works to support his gambling habit. If you like private-eye fiction, Anthony's books are worth a look.