Tonight 50 years ago, CBS aired S06E22 "Mother's Deadly Helper".
The episode centers around Lester Smith (Anthony Zerbe) who has had it with the judicial system being soft on criminals. Smith takes things too far by gunning down one guy after he's released by the judge - outside the courthouse no less! He takes out another paroled convict by whacking the dude on the head and hanging him.
Smith writes letters to McGarrett bragging about helping him and Five-O with these criminals. Five-O does everything possible to track down 'Mother's Helper', which is how Smith is signing the letters. McGarrett even makes the uncomfortable decision to go on TV and discuss the criminal judicial system with Freddie Dryden (Casey Kasem). There is a really good debate between the two.
Smith sees the TV interaction where McGarrett baits Smith. Five-O nearly corners Smith at a cemetery but Smith gets away. The next move that Smith makes is to kidnap a judge. Judge Bergstrom (Frank Cady) had just released two youthful, first-time offenders. It pushes Smith over the edge and he gives Five-O a deadline.
Fortunately, Five-O figures out where Smith is and surround the guy. They take him in but not before he throws a trash can at McGarrett's head and drawing blood. Smith vows revenge as he's being dragged away.
Mr. Mike has much more detail in his review: https://www.fiveohomepage.com/5-0log6.htm#142
This is a good episode and the first time I watched it on MeTV in 2017/2018, I was floored, but not for the reason you may think.
There are a lot of familiar faces in this show including Kasem who is having something of a crazy hair day. Along with his guest appearances in Five-O (he also guested in S07E04 "Steal Now – Pay Later"), Kasem was a prolific voice actor. He did a lot with Hanna-Barbera in the 1970s along with voicing the team commander in my favorite series, Battle of the Planets (1978).
Mr. Mike mentions Cady's appearances in Petticoat Junction, Green Acres, and The Beverly Hillbillies. (I knew his voice sounded familiar!)
As well, Zerbe would continue his career and even have a major role in Star Trek: Insurrection. He played Admiral Dougherty who was trying to displace a race due to some unique rings around their planet. What he got was a blood feud. This was one of many roles Zerbe played throughout the years.
One sequence I really like is between Dryden and McGarrett. They're polar opposites when it comes to the judicial system and I was in a Criminolgy class at the time. It was a very cool exchange.
The only thing I would knock this episode on is the warp-speed postal service. I've not known any postal services that move that fast!
Happy 50th, "Mother's Deadly Helper"!!!