The creator of the series, Roy Huggins, is responsible for several other important shows, including City of Angels and The Rockford Files (plus a number of other individual episodes and movies). His novel The Double Take is a wonderful late 40's hard-boiled private eye story, somewhere between Raymond Chandler and Ross McDonald.

http://therapsheet.blogspot.com/2009/01/book-you-have-to-read-double-take-by.html