"The Ice Cream Man" with Clint Howard? That's one of my alltime favorite movies, personally. There's another one, a little more popular, but I've never seen it.
As far as understanding it, Greg was let out of the sanitarium, and took up a job as an Ice Cream man, and he just reverted to being a child killer who used kids in his ice cream.
"It's grenadine!" 😂 😂 😂