Warning! SPOILERS for The Walking Dead season 10 ahead!
The identity of who released Negan from his cell in The Walking Dead season 10 remains a mystery, but there's strong evidence to suspect it was Carol who released Negan as part of a bigger plan. Since his escape, Negan has found himself in the company of the Whisperers, and while this looks like the survivors' enemies are joining forces, the new arrangement may not be as dire as it at first appears.
The Walking Dead season 10 began by suggesting war would soon break out between the survivors and the Whisperers, but since then, the two sides have more or less been waging a cold war. A couple border crossings here, a few waves of walkers there, and tensions continue to rise. But with only two episodes of The Walking Dead season 10 left to go before the mid-season break, one side is sure to make a move soon. Unless, of course, someone has already made their move and is now just waiting for the plan to unfold.
Upon Negan's escape in The Walking Dead season 10, episode 4, "Silence the Whisperers", there were a handful of possible accomplices. At first, Lydia seemed the most likely suspect, even admitting to releasing him, but her confession was quickly refuted by Daryl. Another potential suspect was Brandon, Negan's guard and Savior super fan. In fact, The Walking Dead even strongly hinted it was Brandon, and considering Brandon is who releases Negan in the comics, it made a certain amount of sense. But then in the following episode, "What It Always Is", Brandon says he doesn't know who released Negan, leaving the culprit's identity a mystery. However, there is one character with a strong motive for releasing Negan and it's Carol.
Theory: Carol Released Negan
Carol has a surprisingly low profile in The Walking Dead episode that sees Negan escape. She's still recuperating from her run-in with the Whisperer during "Ghosts", and spends much of the episode holed up in her bedroom. The one scene in where she does appear, Carol is seen sitting on the front steps of Daryl's house and the two briefly chat. This leaves a lot time during "Silence the Whisperers" that Carol is unaccounted for, and it's possible she uses this to her advantage.
Lydia is ruled out as a suspect for releasing Negan because Daryl claims he would have known if she had left the house. That's certainly true because Daryl is concerned for Lydia, and after her traumatic night, he would have kept an eye on her. The same can't necessarily be said of Carol, and if there's one person capable of sneaking passed Daryl unnoticed, it's her. Not to mention, she's strangely unconcerned about Negan's escape when Daryl and her later discuss it, quickly moving the conversation to what she considers to be the real threat - Alpha.
Why Carol Released Negan
Margo's death turns everyone's attention back to Negan and away from the bigger threat posed by Alpha and the Whisperers. Holding a trial for Negan could divert their focus for even longer. Carol wants everyone's focus on Alpha, and that means she needs to get rid of Negan. But rather than kill him - an efficient though reckless option that would likely only distract everyone even more - Carol releases him.
Of course, Negan's escape doesn't go unnoticed, but the manpower and time spent searching for him is less than what would have been needed for a trial and possible execution. Plus, interest will wane if it takes too long to find him. Most importantly, though, needing to search for Negan gives Carol a cover story for what she really wants to do - search for Alpha's horde. And in The Walking Dead season 10 episode, "Bonds", she does exactly that. Releasing Negan hasn't just removed him as distraction from the real enemy, it's given Carol an outlet to carry on with her own plans.
Are Carol & Negan Working Together?
That in itself may be enough for Carol: release Negan to get him out of the way and use searching for him as a guise to find Alpha's horde. But Carol is a resourceful woman, and if given the opportunity to use Negan against Alpha, she may take it. In which case, Carol's releasing of Negan and sparing him from either death or lifelong imprisonment may have come with a request - kill Alpha. It is Negan, after all, who kills Alpha in The Walking Dead comics, and if the AMC series is going have him do the same, it will need to create a scenario in which it makes sense.
The Negan of the comics and the Negan on AMC's The Walking Dead are different characters by this point, but killing Alpha can still be a stop on his path towards redemption. In "What It Always Is", Negan's decision to cross the border and seek out the Whisperers may not have come from his anger or grief. Negan didn't plan on Brandon following him or finding that mother and son, and once they're gone, there's nothing else for him to do but wander in the wilderness. Nothing, that is, but carry out Carol's request.
Carol's sole focus in The Walking Dead season 10 is to get revenge on Alpha and releasing Negan, it may turn out, is an important step in reaching her goal. She's removed him as a distraction and created an opportunity to continue searching for the horde. If Carol and Negan are actually working together, then his recent infiltration of the Whisperers is just another step in the plan. But even if he's joined them of his own accord, a wild card like Negan is sure to still cause problems for Alpha. Either way, it all benefits Carol and her quest for revenge.
The Walking Dead season 10 continues Sunday, November 17th with "Open Your Eyes" at 9pm/8c on AMC.