If Hannibal season 4 ever materializes, and fans sure hope it does, Jack Crawford may be in a position of having to hunt his protege Will Graham. Of all the various adaptations of Thomas Harris' Hannibal Lecter books, the character relationship that's stayed the most consistent is that between Will and Jack. While Jack is Will's boss at the FBI, he's also much more than that. Jack is in many ways a surrogate father figure and mentor to Will, and clearly cares a lot about his well being.
On the other hand, Jack is such a committed lawman that sometimes he can get quite overzealous in his attempts to bring killers to justice. As skilled a profiler as Will is, and as good as he is at getting inside the heads of psychopaths, Jack knows he's also not far from the edge when dealing with such cases. Yet, Jack still employs Will's services, because sometimes he feels Will is the only investigator skilled enough to catch particularly elusive killers.
To that end, as close as Jack and Will tend to be, their personal and professional relationships are perpetually on the brink of disaster. Will knows Jack might be risking his sanity by getting him involved in cases like The Chesapeake Ripper, and Jack knows will knows, but both men opt to take the risk if people might be saved from a grisly demise. At the end of Hannibal season 3 though, Will's ongoing mental collapse reached its seemingly inevitable conclusion.
Hannibal Season 4 Theory: Jack Crawford Will Hunt Will Graham
Since it's been made clear by creator Bryan Fuller that Hannibal and Will both survived the fall off a cliff at the end of season 3, which was hinted as much by the final scene involving Bedelia Du Maurier at a table set for three, it seems likely that Hannibal and Will will still be together if and when season 4 begins. Their shared murder of Francis Dolarhyde looked to finally make explicit the romantic bond that had been developing between the two characters for quite some time, so there's no reason to expect that spark to fade, at least not right away.
With that in mind, it's only a matter of time before one or both of them begin claiming victims, especially Hannibal. Will may be reluctant to kill more people, but Dr. Lecter definitely won't be. Once it's clear they're still at large, Jack Crawford will make it his personal mission to hunt them down, Will specifically. While Jack certainly wants to catch Hannibal and put him back in a cage, his real concern will be Will, as he'll blame himself for Will succumbing to the dark side and being seduced by Hannibal's attempts to bring out the killer within him.
While Jack's pursuit of Will will begin in the hopes of finding him, breaking Hannibal's spell, and rehabilitating his former friend and colleague, there's a chance Will won't want to be found or helped. If Will becomes an accessory to further Hannibal murders, Jack may be forced to begin looking at him as a target and not a victim, no matter how much he might not want to. This will set Jack on the most personal investigation he's ever conducted, with the highest stakes.
Hannibal Season 4: What Might Happen Instead
Of course, there's always the possibility of Hannibal season 4 bucking the above theory and going somewhere entirely different. Perhaps Will won't take as long to revert to his old self as one might think, quickly becoming disgusted at what he's done under Hannibal's influence, and what he'll surely continue to do if they remain together. He may well truly love Hannibal, in some dark twisted way, and Hannibal may truly feel the same, or at least as close as a sociopath can come to that feeling. Before he met Hannibal though, Will would've never considered murdering someone, even a suspect, unless his own life was in danger.
If that moral, ethical Will Graham still lives inside the man who's spent three seasons getting further and further inside Hannibal's web of cannibalism and murder, he likely won't stand for being part of whatever horrors Hannibal decides to start inflicting on those Will would deem undeserving. At that point, Will may actually choose to reach out to Jack himself, offering to turn himself and/or Hannibal into custody. Hannibal obviously wouldn't go along, and a big battle involving all three men could be in order.
Hannibal Season 4: What's Most Likely To Happen
As for what's most likely to happen in Hannibal season 4, it'll probably come down to a little of both scenarios presented above. Jack may well hunt Will, whether he sees it as a rescue mission, a mission to stop a killer, or both. However, Will may also find himself committing atrocities alongside Hannibal for a brief period, or at least turning a blind eye to them, but it's only a matter of time before Will snaps out of it, if only for his wife Molly, who fans often tend to forget about amidst the obsession with Hannigram.
Also, for as much as fans love Mads Mikkelsen's mesmerizing portrayal of Hannibal, it's important to remember that he's evil to the core. Sure, he's sometimes the lesser of two evils, such as with Mason Verger, but he's still not someone any actual person would ever want to know. If Will betrays Hannibal, Dr. Lecter would be very likely to make him his next meal. Hannibal may some type of affection toward Will, but the feelings of a murderous cannibal have their limits.
In the end, Jack will likely pursue Will and Hannibal for a while, possibly up to half the season. But eventually, Will and Hannibal's tenuous relationship will crumble, leaving Will wanting to become the man he once was, and not the monster Hannibal wants him to be. The question is, will Hannibal allow that, with the likely answer being no.