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Almost any episode where a police officer is killed on duty.
"Twenty-Two Rifle for Christmas", a Christmas Episode that was made for both the radio and TV versions, teaches An Aesop about the dangers of giving guns to children as gifts—in the harshest way possible. Stanley Johnstone finds the rifle his parents bought him for Christmas. He loads it and takes it to show to his friend Stevie Morheim. While the children are playing with the gun, it accidentally goes off, killing Stevie. Stanley takes Stevie's body to a nearby cave and prays for God to bring his friend back to life, but it doesn't work. When Stevie's father is told, he breaks down sobbing, babbling about all the nice gifts he bought for his son—gifts he decides to give to Stanley.
"The Big High" - an elderly gentleman asks Friday and Gannon to talk to his daughter and her husband about their marijuana use, worried that their behavior is putting his infant grandson in danger. After several debates with the couple throughout the episode, Friday and Gannon get called back to the residence and find everyone whacked-out on drugs. Friday asks where the baby is, and the Mom remembers she put him in the tub. They rush upstairs, only to find out it's too late. Gannon literally runs out of the bathroom because he's going to be sick at the sight.
One episode involving a child abuse case begins with Friday detailing several cases of abuse to a woman from a local community organization. She truly had no idea how awful abuse cases could be as she breaks down in tears after Friday and Gannon leave when she asks to be alone and collect herself. Even Friday was having a hard time maintaining his professional attitude while outlining the details of each case.
The episode "The Big Hammer" from the 1960's revival. The landlord of an apartment was found bludgeoned to death by a claw hammer. Gannon and Friday are questioning an elderly man who lived in the apartments, and who went with the victim every Wednesday to lay flowers on their wives' graves. After they finish questioning him, the man mentions that Wednesdays will be a lot longer now, because now he has three graves to lay flowers on. It's the man's absolutely heartbroken, verge-of-tears expression that makes it.
"The Starlet" from the 1960s revival had Friday and Gannon searching for a 16 year old girl who ran away and came to LA to be in the movies. She succeeded, too bad it was in porn. At the end, they find her in her room in a dingy rooming house lying on a matress on the floor, having killed herself with a fatal overdose. By her side was an envelope adressed 'To whom it may concern.' The letter inside had the words, 'To whom it may concern' and nothing else.
"The Big Children" has Friday listing the details he has to write on a death report for a neglected and abused 22 month old toddler.
"The Big Producer" qualifies, although more in the TV version than the radio. A former movie maven who was been reduced to making porn and selling it to high schoolers relives his glory days in the abandoned (or underused for the radio version) studio where he shot his now forgotten films.
In "The Big Barette", we see the murder victim's funeral.
Joe Friday cries exactly twice over the entire course of the series: in the radio episode "The Big Sorrow" and its subsequent adaptation for television. The episode was written immediately after the sudden death of actor Barton Yarborough; Jack Webb decided that it was only right that Romero go out the same way as his portrayer and much of the episode deals with the sad fallout from Romero's loss. There was more to it than pure acting - Webb and Yarborough were good friends.
"The Big Bar" deals with a robber of bars who, after claiming all the cash, shoots the bartender anyway. In one scene, the widow of one of the bartenders is trying to come to grips with the fact that her husband has been senselessly, violently murdered in front of her.
Any scene in General Receiving Hospital where a priest is called in—it means there's nothing the doctors can do.