Let’s take a look at what we do know about the cabin.
We were first introduced to the Cabin when Ben took Locke there to “meet” Jacob. Ben proceeded to talk to an invisible chair and tried to pursuade Locke that Jacob was sat in the chair. Just as an unimpressed Locke decides to leave the Cabin, all hell breaks loose. Things begin to move around the room, things break etc. and Ben is pushed accross the room and we see for a split second someone sat in the chair. We also here someone saying “Help me”. Locke is the only one who hears it and this then annoys Ben. In Season 5 we find out that Ben had never even met Jacob, and when he took Locke to the Cabin he was pretending to talk to Jacob in the empty chair.
Another thing we know about the Cabin is it is surrounded by an ash ring, which at some point gets broken. From meeting The Temple Others we know that the ash was used as protection against The Smoke Monster / MIB. So, the ash around the Cabin was either keeping Smokey out, or keeping Smokey in.
My theory is, it was used to keep Smokey out. Smokey was surveying the island since The Pilot and I think the ash circle around the Cabin was broken after that time (more on that later), so it couldn’t have been used to keep Smokey in.
So, if it was to keep Smokey out, was it really Jacob in the chair? My answer is no.
Think back to Room 23 – the “brainwashing” room that we’ve seen. We know that was a part of some Dharma experiment, and I think that this room is somehow linked to The Cabin. I think that whoever gets put into the “brainwashing” chair can somehow project themselves to The Cabin. At that moment when Ben and Locke are at the Cabin, no one else is present in the room. But around that time someone is being “brainwashed” in Room 23. I’m not entirely sure who, but whoever it was was able to project themselves for a couple of seconds to The Cabin when Ben and Locke were there, and asked them for help.
Walt was also being “brainwashed” when The Others kidnapped him, only Walt is “Special”, and was able to project himself in places where is wasn’t supposed to be. That is, any place in the world, any place in time. I’m going off the subject, but I believe that when Walt appeared to Locke and told him he had work to do, this was when he was being “brainwashed” in Room 23. I know he wasn’t on the island at that time, but when we was being “brainwashed” he could project himself to the future. He could also project himself to the past (when Shannon saw him).
Anyway… back to The Cabin. Ben knew of the Cabin, he’d helped with some of the experiments, but he’d only ever witnessed things that happened at Room 23. He’d never seen the effects of these experiments at The Cabin. So when he went there, he never expected things to start flying around the room and was just as in shock as Locke was.
So, why didn’t Ben hear the voice ask for help? That, I believe, is down to Jacob.
Long before the experiments started, Jacob used The Cabin as a place to go when he was bored of looking out to sea. He placed the ash around it to prevent his brother from going there. When Dharma came and found the Cabin they decided it would be a great place to try their “brainwashing” experiments. They didn’t touch the ash. They knew something or someone had placed it there for a reason and didn’t want to tarnish it.
However, after The Purge, instead of getting his cabin back like he’d hoped, Ben and the Others decided to make use of the “brainwashing” technology. So, because of Ben’s involvement, Jacob punished him by not allowing him to be so “in-tuned” with the Island. On this miracle Island Ben got a tumour, he had to have an operation to have it removed and took a week or two for him to fully heal. Jacob made him like this.
So when a voice said “Help Me”, Ben couldn’t hear it because he wasn’t as “in-tuned” with the Island as Locke was. Of course, Ben had a hissy fit when he realised just how special Locke was when Locke told him he’d heard someone in the Cabin. Ben knew it was part of Jacob’s punishment.
When Illana and her crew arrived at the Cabin, they were expecting to find Jacob there because he had used it often before Dharma showed up. When they saw the break in the ash circle they knew that it’d been used by MIB and that’s why they burnt it down.
Locke broke the ash circle when he and Ben left The Cabin. When he broke the ash it caused a temporal anomaly due to the power of the ash and the experiments that had happened there. Just like Room 23 allowed its victims to project themselves to The Cabin, The Cabin was also able to project itself somewhere else on the island. But only for a short amount of time, and only once the ash was broken. When Hurley stumbled upon The Cabin it had already taken occupancy by MIB (in the form of Christian Shepherd). But it was still shifting around on the Island which is why Hurley saw it in two different places in a short period of time.
MIB was using The Cabin as part of the bigger plan to kill Jacob. He knew that Locke now thought it was Jacob who had asked him for help, so he knew he could manipulate Locke on his next visit to The Cabin.
But who was the person that peered through the hole and looked at Hurley? It certainly looked like MIB was with company. However, I think it was just a trick of MIB’s. He can turn himself into anyone who has died on (or off) the Island, and he knew Hurley was looking through the hole, so he thought he’d have some fun and stare back at him. Only, it wasn’t Christian Shepherd’s form staring back at him, it was someone Hurley knew who had died. (I wanted to say his grandpa but I know it looked nothing like him, and can’t think of anyone else in particular).
So, The Cabin. Mystery Solved?