Unfortunately, this only deepens the mystery further, for all that it contains is a piece of paper upon which is written an address - signed with the initial "MZ". Little do you know, that this seemingly innocuous piece of correspondence is about to take you on the greatest adventure of your life...!
You wait, but after half an hour, there is still no answer. You are about to walk away, when the door is opened by a young man with upside-down eyes.
"Allow me to introduce myself. I'm Mark Zuckerberg, from Facebook, and I've invited you here to witness the first demonstration of my new invention! Come on - it's nearly time for that to happen!"
"OK," you say.
"Well, this is it," he belches, between gulps of air. "It's a wrist-mounted time machine. Pretty cool, huh?"
"Yes," you reply.
"Facebook is used daily by billions of people. Everybody has it, so there's no more room for market expansion. The only way to expand Facebook's reach is to think four dimensionally - by expanding into the past!
"Once the time machine has been synced with your Facebook account, you'll be able to send friend requests to anyone in history - even Marco Polo, and Sonny Bono!".
You instinctively reach out your hand to stop Zuckerberg, but succeed only in inadvertently activating the time gauntlet.
"You crazy horse!" shouts the Facebook creator, over the noise of the time stream. "I hadn't yet inputted a date - we could find ourselves anywhere in history! What if we land in the middle of the Poll Tax Riots, or a famous car crash?"
He looks around, to take in your surroundings. "I wonder where we are? It looks like some kind of - "
But before Zuckerberg can finish, a shrill voice pierces the air.
You turn around to see the infant Adolf Hitler goose-stepping into the room.
"Holy cows!" yelps Zuckerberg. "Do you know who that is? That's Adolf Hitler as a baby!"
"Addykins Hitler to you, meinen freund," seethes the tiny Nazi.
"We're no friends of yours, pal," replies Zuckerberg. "We're from the future. You grow up to do some real bad stuff, and I'm gonna put a stop to it, before it has even happened - by strangling you, even if you are a baby!"
"Killing me might destabilise the entire time stream. Surely you have heard of Ze Butterfly Effect?"
"The film starring Ashton Kutcher?" asks Zuckerberg.
"Ja" snaps the little Hitler. "Wipe me out before I've committed my war crimes, and you mighten returnen homen to finden ze worlden overrun by giant evil butterfliesenliebermilchen."
"Dammit," curses Zuckerberg. "He's right. We can't risk it."
"Ha ha ha," says Baby Hitler, with a laugh, as he takes a victory lap of the nursery.
"I might not be able to kill you," insists Zuckerberg, "But I can still do this!"
Zuckerberg quickly spits at baby Hitler, before reactivating the time gauntlet. Instantly, you find yourself back in the time continuum.
"What a rush," says Zuckerberg. "Wait until my Facebook friends read that I spat at Hitler when he was a baby!"
"You are home," grunts a gravelly voice. "This is where your home will one day be built."
"What the?!" questions Zuckerberg, as you are faced with a heavily-browed Neanderthal. "A c-c-c-caveman!"
Zuckerberg starts to back away, stammering, as Ug Zuckerberg lifts a big stone above his head: "But if you kill me, I'll cease to exist. It'll be a temporal paradox!"
"I don't understand what you're saying," says Ug Zuckerberg. "I am merely a simple caveman, and as I said previously, I intend to crush your face in with the big stone - because that's how I roll!"
"Hah!" replies Mark Zuckerberg. "Didn't you hear? A rolling stone gathers no moss!"
"What?" asks the caveman, confused.
Zuckerberg quickly reaches into his pocket, and brings out a little pot of talcum powder. Before his ancestor can react, Zuckerberg has squirted him in the face with the talc! As the caveman coughs and sputters, Mark Zuckerberg reactivates the time gauntlet.
"Phew!" he says. "That was a closey! Wait until my Facebook friends read that I talc-ed my ancestor!"
"Gosh darn it," curses Zuckerberg. "We're still not back home. How long is this nutty romp going to take?"
"It doesn't matter how long it takes," says a voice. "After all - don't you have ein time machine?"
You both spin around to find yourselves face to face with... the grown-up Adolf Hitler!!!
"Ich bin Adolf Hitler now," says Hitler, "And I remember you two - und how you spat at me, und vanted to kill me. It inspired me to grow up to get in Das Guinness Book of Records for being one of der most awful people who ever existed. Zo in some respectenischens, I owe everything to you!"
"Oh man!" gasps Mark Zuckerberg. "We inadvertently created Hitler! By saying that we wanted to kill him, but not actually doing it, we provided the inspiration for his crimes!"
"Ja!" laughs Hitler. "How's that for irony, mein kleine Englischer pig dogs? I can't thank you enough, thus I have decided to throw ein banquet in your honour!"
"No way!" trills Zuckerberg. "If word gets out that Adolf Hitler threw a party for us, I'll never live it down! We gotta do something!"
"Ouchen!" barks Hitler. "Vot ist thou doink?!"
"I'm ripping off your famous moustache, Adolf!" coughs Zuckerberg. "Let's see you desire to throw a party in our honour now!"
"You bloody bastard!" shouts Hitler, as Zuckerberg rips the moustache off his face, and tosses it to you. "Look at meinen face! Everybody can see meinen philtrum!"
"Yes they can," replies Zuckerberg. "And I'm afraid we can't stick around to watch you grow a new moustache. Later, Addykins!"
The last thing you hear before you and Mark Zuckerberg re-enter the time continuum is a furious Adolf Hitler shouting: "Do not call me Addykins!"
"Yes," you reply.
"Well, anyway, I'm going to destroy the time gauntlet," says Zuckerberg, picking up a hammer. "The power of time travel is far too open to abuse. The last thing Facebook needs is someone like Adolf Hitler trolling and cyberbullying through time - like he hasn't been annoying enough already!"
And with that, Zuckerberg smashes the time gauntlet to pieces.
"Yes," you reply.
You pull out your hand, to find that you accidentally brought Hitler's moustache back through time with you.
You decide you're going to stick it to a bit of card, and mount it on your mantlepiece - so that you never forget the radical adventure you went on!