I've just managed to put together a set of wires and components that should allow me to recharge the laptop using my arc reactor, when a bright spot of light appears at the far end of the room. It's Mark IV's super-LED, carried by Mark II, who runs to our side.

"Guys, you need to see this," he announces.

"We're sort of in the middle of something important here," I tell him. "And we've got some pretty scary news as well."

"I doubt it can be as scary as this. Come on," he beckons, so Mark I and I leave the laptop and the makeshift power adapter waiting on the floor and follow him. He leads us to a set of doors in the concrete wall - two thick blast doors and an elevator to the right of them. The blast door in the middle is wide open.

"The door to the left is completely stuck, and it might not lead anywhere even if we'd manage to open it. The elevator's out of order, of course," Mark II explains, and without wasting more time, enters the doorway that's open. It's actually the beginning of a narrow corridor that slopes gently upwards. The walls are bare. On the ceiling, I can spot emergency lights that aren't on.

After what feels like at least ten minutes of walking, Mark II tells Mark I to turn off the light. As Mark I does that, Mark II does the same. Without the artificial lights, we can see natural-looking white light at the far end of the tunnel. I don't know what's waiting for us out there, but the way Mark II is acting about it makes me uneasy. If he thinks it's scary, there's a good chance I'll think so too.

At the end of the tunnel, there's a blast door that's even more massive than the ones we've already passed. It's open, but only a crack just wide enough for one person to pass through at a time.

"We found it open like this," Mark II notes.

"That's probably because Mark V went this way," I tell him.

"Mark V?" he asks, surprised, but I don't answer him, because by this time, we've stepped out, and all I can do is stare at the view in front of us.

The first impression I get is that we're surrounded by snow and ice, that we're in Antarctica or the Arctic. Everything's white. But the ground is almost level, wavy with some low dune-like formations, and it's not freezing cold, just slightly chilly, maybe around 50 degrees F. The sky is completely white as well, not with bright light, but a bleak, grayish white, like on a day so cloudy that the sun's not visible at all.

Mark I has crouched to the ground and is running his fingers through what I took for snow. I look more closely, and see that it's actually fine white sand. The dunes I can see are real sand dunes. And there's nothing else here as far as the eye can see: white sand and white sky. The entrance to the tunnel behind us is just another white dune, but with a dark doorway in it. It's a landscape so unnaturally lifeless and featureless that it's right out of a nightmare. A stark landscape. Ha ha, very funny. Not.

"This world is empty," someone to my right says in my voice. The tone is as desolate as the view in front of us. I turn to look which one of us is speaking. It's Mark IV, whose blue eyes are turned towards the cloud-covered sky.

"Uh, are you trying to tell you can somehow detect all the people on the planet?" I ask him. "Because if you are, I don't believe you."

"Not exactly," Mark IV answers. "I wouldn't know about people, but I do know that there's nothing electronic that I can reach anywhere on this world, and that's not a promising sign. No satellites, no cell phones, no computers, nothing at all."

"You can remotely connect to satellites just like that? You expect us to believe that?" I'm still very suspicious.

"Extremis abilities. Believe what you will, but this world is empty," he repeats. What he claims sounds pretty incredible, but then again, I'm a pretty incredible guy. If anyone could somehow develop such an ability, it would be me. Or a version of me, anyway.

"So, there's a good chance the whole planet actually looks like this," I think out loud. The dark words of Mark V's note ring in my mind, and I feel chilled to the core. 'I am to blame for what happened.' He caused all this?

"Like this, or otherwise just as dead," Mark IV says gloomily. "Mind you, there's no reason this has to be Earth."

"If it's not Earth, then we've done time travel, space travel and parallel universe travel all in one to get here. Doesn't sound plausible to me," I state. "And considering the stuff we found down there, I'd put my money on this being good old Terra."

"Have any of you considered that no matter what planet this is, it could be full of radiation or other environmental hazards we can't see or feel?" Mark I points out.

"Yes, we did consider it when we found our way here, and it's perfectly possible, but the door was already open. We decided that the most important thing was to find out where we are, because it might help us figure out how to get away from here," Mark II answers.

"Except that it doesn't," I remark. "All we know is that we're in the middle of a featureless white desert in a world that's empty of anything electronic, according to Mark IV. I bet the stuff me and Mark I found is more useful."

"You mentioned something about a Mark V?" Mark II reminds me.

I nod, but I need to check one thing first. "Do either of you lead a company called 'Stark Corporation'?"

"I've got Stark Solutions, and then there's Stark-Fujikawa, it's pretty complicated, but no, I don't think I've even heard of anything called Stark Corporation," Mark II says.

"Actually, I'm Director of S.H.I.E.L.D.", Mark IV declares.

Again, there's one of those stunned silences where we Marks I-III just stare at Mark IV, and then, after a few beats, speak up all at the same time.

"You're kidding, right?" Mark I asks.

"Have they gone crazy?" Mark II asks.

"What, you're the local Nick Fury?" I ask.

This time, Mark IV doesn't seem to relish our amazement. "I'm definitely not Nick Fury, and I'm not sure I'm doing a very good job... Hm," he gazes at the three of us thoughtfully, "I guess a lot of the bad stuff that has taken place in my universe hasn't happened in yours."

I can't help but wonder what year Mark IV is from - maybe he's from some dark distant future, that would explain his advanced abilities too. I 'll ask him about it later, now I want my initial question answered. "We can compare notes later. No Stark Corporation in your universe either?"

Mark IV shakes his head. "Not that I know of."

"Well, then, unless one of us is lying, there's one more of me... us, I mean, who's a major player in this drama of ours. Hence, Mark V."

"He left us a note," Mark I adds, and hands the piece of paper to II and IV. They read it through, and I can see their expressions change as they take it in.

"Could it mean that this..." Mark II motions at the white wasteland around us, clearly shocked. "This is Mark V's fault?"

"Well, he seems certain he's done something horrible," Mark I says.

"The note was under his laptop, which supposedly has some data that could explain some of this. I'm going back inside to try to figure it out," I nod towards the doorway.

Mark IV has been gazing at the horizon silently for a while, as if searching for something. He sighs. "I guess there's no point in trying to find Mark V. We don't know how long ago he left and which direction he picked, and we'd just get lost out there."

"He's the most likely villain of the story anyway," Mark II says. "We might not want to meet him."

Mark IV shrugs. "I don't know. Maybe he never meant for anything bad to happen. We're not perfect, after all. We make mistakes. Sometimes the consequences can be devastating."

That, and the grim situation we are in, leave us all silent again. We walk back into the tunnel in single file, in numerical order - Mark I first, with his chest beam spotlight, then Mark II, me, and Mark IV, who hasn't lit his super-LED, so we're in the dark. I don't complain about it. It kind of fits the occasion.