I initially rejected the idea of placing this episode among the top 10 in the series but as I was going through the shows another time around I was surprised to be looking forward to watching "To Walk with the Serpent" again, despite that the episode is unsettling and outside the usual Route 66 spectrum in the same way "The Thin White Line" is easily distinguished from the rest of the series. Aside from the jaunty, oddly appropriate background music - which, I believe is featured in no other episode - I realized the supporting cast is what makes this particular episode uniquely interesting and oddly compelling. Dan O'Herlihy is outstanding as the charismatic lead; the great Simon Oakland makes his only series appearance; Joe Campanella plays an FBI agent with his usual distinctive voice and flair; and even Frank Sutton, famous for playing Sergeant Carter on Gomer Pyle, is excellently cast as a psychopathic lackey. Martin Milner does an excellent job as he seems, at moments, to be pulled into a philosophy at odds with Tod's usual demeanor. An additional note: those who appreciate O'Herlihy's performance here should, if they haven't watched it, see his similarly eerie performance in the movie "Fail-Safe." In short, "To Walk with the Serpent" will stick with a person.