I haven't seen this episode in decades, but remember it well. Barnaby right off the bat seems to know who the killer is, but drops those "little" hints along the way to make the guy sweat it out, which is always fun. Tag it the Columbo method. Actually, if you are a TRUE mystery fan, the idea originated with the great CHARLIE CHAN movies. Nobody did it better than Charlie. Also watch Barnaby's facial expressions, his eyes narrowing, when his suspicions begin to set on a certain suspect. They're toast.
The villain is well played by tall, lanky Andrew Prine, one of the master tv villains. The clever death trap here is a rattlesnake on the loose, killing rancher Ford Rainey (a regular on MANNIX). Young Vincent Van Patten, who was growing up fast, plays Kevin, caught up in the homicide and scared out of his boots. I always thought he was a terrific young actor, a natural. He had an impressive role in the very first episode of CANNON a few years earlier. Sharon Acker played his mom.
Also look for Katherine Justice as Liza, Prine's new wife, and veteran Arch Johnson, usually playing a sheriff.
Not a classic, but I would still rate it at least a 9 for a solid cast. Best of the rest pits Barnaby against the snakes in a cave. Watch that scene, and well directed by Walter Grauman. Written by Barry Oringer, long associated with the hit series, HOTEL.
Production notes indicate filming at both Griffith Park and famous Bronson Canyon in Hollywood, the perfect place to meet and greet snakes. For decades, the Canyon was host to westerns and a ton of classic sci fi films. If those caves could talk.
SEASON 2 EPISODE 4. Remastered CBS dvd box set.