The Punisher isn't shy about the mental-health struggles of its characters. While dark, brooding vigilante tales are nothing new (see every Batman movie for proof of that,) the tormented men of The Punisher Season One are tormented for a very good reason. Many of the show's characters, Frank Castle included, are wrestling with Post Traumatic Stress Disorder. While Castle and others seem to still be affected by their time overseas, Castle's fellow veteran Curtis Hoyle serves as an example of how someone can learn to live with their traumatic war experiences. It's clear that Castle and Curtis are close, but just who is Curt to The Punisher and what could he mean for the series?
While there are a few new characters introduced in The Punisher, Curtis Hoyle comes straight from the Marvel comic books. In the original comics, Curtis and Frank served in Vietnam together. Unlike in the Netflix show, Curtis and Frank were not long-time friends in the comics. In fact, he only appears in two issues of The Punisher before Frank throws him out of a plane. Of course, Curtis didn't do himself any favors by trying to kill Frank after jeopardizing a criminal operation. It seems the only thing that the Punisher Netflix show borrowed from Curtis' comic appearances were his name and having served in a war with Frank.
In the show, Frank Castle and Curtis seem to be close friends. At least, as close of friends as someone can get with Frank Castle. After Frank has all but fallen off of the face of the Earth following the events of Daredevil Season 2, Curtis seems to be one of the only people who knows Frank Castle is still alive. He also pleads with Frank to try and find healthier ways for dealing with his PTSD than taking it out on other people.
When Frank's old friend isn't trying to help him, he's busy helping other veterans who returned from the military to find that you can take the man out of the war, but you can't always take the war out of the man. Curtis' most obvious sign from his experience in war is a missing leg – but many of the men he works with are dealing with internal scars. The veteran PTSD support group that he runs introduces him to Lewis, a young man who is struggling to adapt to non-military life who seems to play a big role in the plot of The Punisher — even if no one knows it yet. Curtis seems to be the connecting tissue in many people's lives, and everyone around him is usually trying their best just to lead a normal life.
While The Punisher is primarily the latest extension of Frank Castle's revenge tale, it also dedicates a lot of time to looking at the effects that war can have on different people. Some turn to violence like Frank Castle, others are lost like Lewis, and some dedicate their time to helping others as Curtis does. He seems to be a genuinely good influence in Frank Castle's life – but that may end up being bad news for Curt.
Things have a tendency to go poorly when someone is friendly with vigilantes, especially when they're as violent as Frank Castle is. As if that weren't enough, there's a government conspiracy going on that is connected to Frank's past – which means that Curtis may end up getting roped in. While he has tried his best to leave war behind, it looks like Frank may inadvertently subject his friend to a very different world of violence. Frank Castle seems to believe that good things cannot survive in the world, but only time will tell if Curtis Hoyle can truly manage to leave their shared, violent past behind.