"From the darkest bowels of Riker's prison, the old men preside over their empire. Nothing goes down without their say-so; no one draws a breath without their permission. And when a riot explodes, they need only fortify their defences and ride it out. But someone else is weaving his way through the bloodstained halls, their newest neighbour: Frank Castle."
The Punisher gets himself sent to prison. He likes it there. All his prey, in one place. There are, though, five old men he's particularly interested in. They've been together for a long time, but under stress situations (aka. the Punisher) some cracks in their relationships might show. And, of course, these are people who kill at the drop of a hat.
The results are everything you'd expect them to be. The Punisher in prison. An entire world of people as bad as him. Nasty as hell, lots of killing and a strong motivation for him to be particularly homicidal towards his current targets. There's a reason why this story was deemed important enough in the Punisher's mythology to be a standalone release, not just another episode of one of his ongoing series.
"You are stupid, all of you. Comparing your pathetic stories. If you were not so blind you would see exactly what this is. No one would go to such lengths as this man has, not even for the worst atrocity. I have done things in my time that make you look like saints, and I am no worse than many he has killed without a second's thought. This is something personal. It is vendetta."