I am going to rewatch the episode, because like a PP said, it was the 1st time in a long time I was shocked, and saddened. My theory is, and I will pay closer attention when I rewatch, is the pipes. The pipes were banging and that's when Henry left Lydia. we then notice other people knew about the pipe situation, because Gerry mentioned it to his wife. We see Alpha meeting King Zeke, and innocently making comments about things she overheard others say, so he thinks she is a true resident of Hilltop. She asks his of something, I don't recall, but she needs his help, he throws his arm around her and they walk off. We don't see him again until the end when Lydia runs up and tells him her mom was there and Henry was missing. (I thought for sure is was going to be his head Carol saw, since he got it in the comic)
What if, Alpha, as the citizen of Hilltop asked for his help, and he rounds up a few people he sees along the way, and they go off with Alpha? Why he wouldn't go too would be the wrench in that hole plotline, but it might be what happened. It had to do with the pipes. I don't know why the teenagers would have been there, but maybe they thought they could help in someway.
This is a huge plot hole, because Alpha was "dressed up" as Hilde from Hilltop Colony (even having gone so far as to scalp Hilde's real hair into a makeshift wig).
So, at the very least -- Tara, Enid, Tammy, Rodney, and Addy all should have blatantly recognized that Hilde wasn't "herself." In fact, we even saw Alpha consciously turn away from Tammy/Earl when they walked past her with baby Adam.
Frankie (having moved to Alexandria) never would have met the real Hilde, so she wouldn't have known the difference one way or the other.
Henry, I assumed, was lured away from everybody by hearing the banging pipes. Alpha probably ambushed him and knocked him out.
Presumably, Alpha must have found a blindspot near the perimeter of The Kingdom through which she would have dragged each person out of the faire. I would also assume that she had a bunch of Whisperer minions waiting in the woods, so they could carry each kidnapped person off to the stable while Alpha went back to kidnap more people.
The problem I have is that it just seems logistically implausible that Alpha could lure Tara, Enid, Tammy, Rodney, and Addy far enough away from the faire to incapacitate them and hand them off to the other Whisperers. I would guess she'd have to abduct each of them separately, unless some of them happened to be in pairs when she'd encountered them (e.g. Rodney/Addy, Tara/Enid). But even then, if she encountered a duo/pair of Hilltoppers together, wouldn't that make it even HARDER for her to abduct both members of the pair simultaneously?
I suppose it's also possible that Alpha had a few other co-conspirators (other Whisperers) dressed up in the slain Hilltoppers' (from the beginning of the episode) clothes...but it still seems a bit too coincidental that four of seven original abductees were longtime Hilltoppers. Alpha must have done a lot of Intel to piece together who might be from the same community that had housed Lydia.
Some of the deaths seemed pretty random...but were they? Conceivably, Alpha recognized Tara from when she came to Hilltop's gates for Lydia. Alpha might have also remembered catching a glance at Enid, when they made the Alden/Luke/Lydia trade and Enid went to hug Alden. She saw Frankie talking with Henry, and may have just assumed Frankie was a Hilltopper for that reason. She also probably saw Lydia -- from a distance -- talking with both Rodney and Addy at some point. Clearly, she saw Tammy holding baby Adam (whom Connie had saved).
What's most sickening is that, once Alpha returned to the stable, she probably forced Henry to watch her decapitate the other nine victims...and then saved Henry's kill for last.
Enid was the most shocking death, for me. Honestly, I saw Tara's death in this specific manner coming several seasons ago. Having read the pike scene from the comics, I suspected they would replace Rosita's pike death with Tara, when adapting it to the TV show. If you think about it, that's some dark irony: Tara ended up dying in the exact same manner in which she'd witnessed Hershel die, back in Season 4.
BTW, did anybody notice an "aged-up" Rachel (obviously recast with a new actress, to reflect the time jump), during the signing of the charter? Pretty clever.
