it seems they could have come from a tunnel OR down the ladder. ben said "who left his open?" and at first i assumed that he was referring to the hatch opening that Paulo had come down. but, if that were the case i would think ben would be a bit more concerned that an outsider had come in, and instead they just went about their business. so, maybe he was referring to a door within the hatch that he and juliet would walk through coming from a tunnel and into the monitoring room. and maybe their path never takes them near the ladder at all.

anyways, i didn't catch anything that suggested a tunnel, but there's a lot i don't catch. so, did anyone have anything specific that suggested a tunnel?