No storyline or character is more intriguing than Lydia in The Walking Dead right now. Introduced last season, Lydia is the troubled daughter of Alpha, the leader of the Whisperers. Flashback sequences highlight how Alpha routinely mistreated Lydia from the very beginning of the zombie apocalypse, but that abuse became more evident after the (deliberately) single mother took charge of the Whisperers and supposedly denounced her human attachments. Tempted by Henry's boyish charm, as well as Alexandria's offer of food, a hot shower and not wearing corpse skins every day, Lydia switches sides and leaves her mother to join the good guys.
Recently, however, Lydia's position has come under question. As tensions with the Whisperers rise, residents of Alexandria have soured towards Lydia's presence more than ever before, but the straw that broke the zombie's back came due to Carol's ever-increasing recklessness in her mission to take down Alpha. Realizing that Alpha lied to her people about Lydia's fate, Carol plans to show off the leader's child to other Whisperers and create dissent among their ranks. After encountering Gamma, the scheme appears to have the desired effect, but Lydia hadn't been clued in and reacts badly to being manipulated, comparing Carol's behavior to that of Alpha. Lydia ultimately leaves Alexandria and strikes out on her own.
With this action, Lydia has become a source of great intrigue in The Walking Dead, as she's a rare example of a main character allied with neither the Whisperers, nor Alexandria. Lydia is highly unlikely to skulk back to her mother's doorstep after leaving in such dramatic fashion, but Lydia also clearly feels she cannot stay in Alexandria. While the character may have the survival skills to live alone in the zombie apocalypse, the ominous presence of the Whisperers means that no survivor is ever really without company in this territory, and it's likely only a matter of time before a wandering Lydia is discovered.
Where Lydia goes next could be the move that decides the outcome of the entire Whisperer war. The audience knows that Lydia is morally sound, and her desire at present is probably just to completely forget about both communities, but this is far easier said than done. At some point, Lydia will encounter one side or the other and be forced to make her choice. On one hand, her intimate knowledge of Alexandria and Hilltop could replace the deceased Dante's intel and devastate both communities, but revealing herself to the Whisperers could turn Alpha's followers against her, sparking a Whisperer rebellion. This is why Lydia's next step could prove instrumental in the ongoing conflict. As a third alternative, if a disgruntled Lydia manages to gain access to Alpha's horde, perhaps these frustrations might even prompt her to release this mass of undead and take out all the communities in a single swoop, waving a bloody farewell to all those that wronged her.
Lydia's arc is so fascinating at present because it's something that has no precedent in the comic books. In The Walking Dead's original story, Lydia is defined largely by her relationship with Carl Grimes, and while Henry fulfilled this role on TV at first, he was killed off before too long. As such, a lone Lydia is an unknown quantity, even to readers of the comic books, and her considerable potential as a character is on the verge of being unleashed for the very first time.
The Walking Dead season 10 has plenty of lingering plot threads heading into the winter season, but these are either already depicted in the comics (as with Negan's defection to the Whisperers and Beta's identity) or have been moved onto other areas of the franchise (Rick's fate and the enigmatic CRM group). Other current storylines, meanwhile, are relatively straightforward in nature, especially now that the Dante twist has cleared up some pressing questions. Will Ezekiel die from his illness? Will Daryl and Connie get together? And will Michonne return with some hardcore weaponry? Each mystery is worthwhile, but each is a "yes or no" conundrum. Lydia's disappearance, on the other hand, could lead to a number of storylines, all very different in their focus, and this unpredictability is something The Walking Dead season 10 will need in order to carry interest through to its midseason premiere.
The Walking Dead returns in 2020 on AMC.