I was kind of expecting a flash of light. Or a tingly sensation or an electric shock or a feeling of intense speed, or at least a jolt. Nope. Nothing.
As it turns out, this is because the instant I closed my eyes, Ed-B managed to hit the emergency abort switch, cancelling the experiment entirely. While the "flux" capacitor discharges harmlessly (but wastefully) into the Earth, he shoulders open the elevator doors and strides across to his alternate self. "What the hell are you talking about?"
"I wasn't anticipating your reactions being quite that fast," says Ed-A.
"They're your reactions, Eduardo my boy," says Ed-B. "What about Jen? We're friends, that's it. You know that's all there is to it. Are you saying we get married? And something bad happens?"
"Um, ahah. Yeah. See, the thing is, this was just supposed to be a sort of joke. I just wanted to make the future more interesting for you. I don't really know if anything happens between us and Jen in the future."
Ed-B gazes levelly at his counterpart from the previous universe for a few moments, and then punches him in the face. As Ed-A reels and tries to regain his balance, Ed-B yells at him. "You're messing with people's lives here, Ed! You're messing with your own life. Let this be a lesson to both of us, since we're pretty much identical; learn to see it from the other guy's perspective. I mean, if I can't empathise with myself I can't empathise with anybody." He turns and heads back to the time machine, where I am still waiting, aghast. "Start it again from step 209," he calls to the scientists in the control room overlooking the machine. He climbs in and shuts the door. The countdown starts again from sixty seconds.
"I can't believe I'd do something like that," says Ed as we wait once again. "I'm not that vindictive, am I?"
"I can't believe it either," I reply. "Maybe it's the fact that you're interfering with your own life that made you think it was okay. I mean, ethically it's a lot like experimenting on yourself versus experimenting on others. Maybe you just thought you could take the joke. Or you were trying to introduce some variety into your alternate self's life."
"My life is varied enough," says Ed. "Bah, I can't second-guess myself. We're both thinking exactly the same number of moves ahead. Well, we'll do it differently when it's our turn..."
The timer hits zero, but there's still no flash of light - quite the opposite in fact, for the lab is dark and empty when we arrive, because it's midnight and there's nobody working. That, I think to myself, was pretty painless.
Above us, an alarm starts to wail and flash. After a minute, a squad of marines wearing helmets and body armour troop into the room and aim machine guns at us.
We raise our hands and surrender, as, thousands of miles away, Ed-C and Sam-C's lives begin, very subtly, to diverge from ours.
Interrogation is nightmarish, until the CIA guys arrive - Agents Mulheardy and White, whom we astound by recognizing and calling by name. They explain how the alternate us (us-C) are under observation for potentially world-threatening activities, and how our sudden appearance here while still being somehow under observation in England might have something to do with Ed-C's experiments. Mentally, Ed and I attempt to make sense of things. Now we are the alternate Ed and Sam. Now we have to continue the chain.
Witnessing it all again from the other set of eyes is plain eerie. We are so predictable. I find myself mentally finishing sentences for my counterpart.
It goes almost exactly the same as the previous time around. Disks change hands. Time-travel passwords are revealed. We hand over the electronic blueprints for the time machine, though Ed declines the offer to keep a copy, saying he's unlikely to bother building one of his own. We see our alternate selves off, headed back in time two days and another nanosecond.
There's one major thing we change, though. This time around, Ed's final piece of advice is different. "MARRY JEN."
Ed-C looks astounded, and never even reaches for the abort switch.
Afterwards, I'm infuriated with Ed, but also somehow unsurprised. Maybe he really does think his own life is just a plaything. Maybe he thought he was doing his other self a favour, or when it came to the crunch he just couldn't resist messing with the future.
In the end I say nothing to him, because there's nothing to say. Though we can never find out what happens to the other Ed and Sam, I hope they're okay.
As we take an overnight passenger flight home - no supersonic action this time around, alas - Ed checks his watch to see how much time we've lost altogether, and I try to pretend none of it ever happened, in preparation for resuming our lives where they left off, apparently, nearly three days ago. Between us, we decide not to adjust our birthdays to suit. It'd just be too hard to explain to our families.
The man sitting next to us is understandably curious when we start talking matter-of-factly about our temporal shenanigans. "Excuse me, have you two... travelled through time or something?" he asks.
"No," I answer. "We're actors in an upcoming time travel movie and we like to stay in character." The human mind is a wonderful thing. Implausible though it is, he's far more likely to swallow that explanation than the truth.
It's only when we finally reach Gatwick Airport and start looking for a coach home that a final thought strikes me.
"Where does the chain end?"
"It goes on forever," says Ed.
"But it can't go on forever. Even going back a nanosecond at a time, you eventually reach a time where the Kerrig Facility had never even been excavated. What then?"
Ed glances at me. "Are you sure you want to know?"
"Why do you say that?"
"I figured it out way back while Ed-A was explaining the theory of time travel to us. Frankly, it was the most worrying thing about the whole situation. Eventually, one of us dies. Possibly both."
I open my mouth, but can't say anything.
"You remember how I said that statistically, there are probably a few dozen of us who - just by chance - broke our legs stepping out of the time machine? Take it to its logical conclusion and someone is eventually going to get killed. The time machine makes a one-in-a-trillion malfunction and kills us both. You or I trip over and crack our heads open on the way to the interrogation room. The plane from England to America crashes and nobody survives. Actually, now that I think about it, the weakest link in the whole sequence of events between one iteration and the next is in the very first few seconds. Marines with guns. Somewhere, when you average out over a trillion iterations, one of a pair of us is almost certain to do or say something wrong, and they'll shoot us in response. In fact, four hundred and fifty billion iterations of that event without either of us getting killed is highly improbable. Maybe a few thousand would be more feasible, a million tops."
"So what about the disk? Somewhere back along the line, we lied? We made up the whole disk thing?"
"I'm sure we had our reasons, and frankly, there's no way we can ever find out for sure. There's no use agonizing over it, now. I daresay the alternate Eds will figure the lie out like I did. In retrospect, I guess we aren't to be trusted after all."
"Speak for yourself," I say meaningfully. "...I just wish there was a better way for it to end. Instead of an Ed and Sam a thousand universes removed from ours getting shot by accident."
"Who knows?" says Ed. "Maybe somewhere along the line, the two of us will decide to set up new lives in America instead. Working at that very facility, maybe. Again, we'll never know for sure."
"Time travel sucks," I declare.
"That it does, Sam," says Ed. "That it does. Right now I just want to go home and have a traditional post-adventure cup of tea."
"Maybe I'll call Jen over," I grin.
Ed groans, but he only has himself to blame.