Charlie and Eko enter the hatch, with Charlie STILL saying "careful!" to Eko, so I imagined Charlie saying that the entire way back to Swan station, which sounds about right. If I were Charlie, though, I wouldn't be NEARLY so close to Eko.
Eko starts setting the dynamite in place against the door. For some reason, now is when Charlie starts wondering if this is a good idea at all, and asks Eko what if they hurt Locke and Desmond, or blow up the computer. "You can leave now, Charlie," says Eko, whose dismissiveness is really starting to bug me. Eko sets the fuse, as Charlie decides to spill the beans to Locke, yelling at him to open the door so they can work things out, and warns him that Eko's planning to blow open the blast door with dynamite. Inside the computer room, Locke looks quizzically at Desmond, who smiles confidently. "It would take an atom bomb, brother. Tell him not to bother." Locke asks if he's sure, and Desmond says he is. He looks over at a metal cart with a crumpled top that I don't remember ever seeing before. But I have a lousy memory, and I'm sure someone will correct me if I'm wrong. Besides, something tells me the upcoming flashback might give us some more insight into the blast doors.
Sure enough, in the flashback we see Desmond with the same cart, wheeling it into a doorway. He's now got on an official Dharma jumpsuit. In the kitchen, Clancy is pouring detergent into a measuring cup and stirring it with a paint brush. He asks if Desmond's ready. Desmond says maybe Clancy should do it, whatever "it" is. "Come on, Des. You've seen me do it a hundred times," says Clancy. So Desmond strolls back into the computer room, and touches a couple of bare wires on the control panel together, until there's a spark, and the now-familiar countdown comes on, preceding the alarm and the doors slamming shut, only one door slams neatly into the dent on the cart, and stops about waist-high. Desmond's quite pleased with himself. He doesn't know what Dharma's going to subtract the cost of that cart from his paycheque.
Desmond ducks under the door back into the kitchen, where Clancy has taken his concoction and paintbrush over to the lowered blast door where Locke saw the map. I guess it's too bad they never figured out how to turn on the black light, huh? I guess they're just assuming this ridiculous inviso-paint is working? Clancy explains that the map was Radzinski's idea; he had a photographic memory. Desmond seems to get all snitty of Radzinski, for some reason, like he's jealous of Clancy's former partner for some reason. "Yet for some reason, you never want to tell me what bloody well happened to him."