Blame this.
Shackleton Mold
This is some cutting-edge stuff, to be sure. Shackleton Mold get its name from where it was recently discovered: back in 1915 a set of photo negatives from the Ross Sea Party Antarctic expedition got enclosed in a block of ice, then left frozen for a century. Yes, 1915. Which is to say, several decades before the 1947 Invasion from Beyond that fundamentally altered our microbial ecosystem and made us vulnerable to the Greys‘ genetic attacks. Sure, we fended them off, eventually — but we’ve been doing repair work ever since. The Mold has thus been an absolute godsend: covert recovery specialists were able to get a sample of the stuff before it got contaminated, which gives us a baseline for what our DNA looked like before we all got infected.
And that means, of course, that we now have some hope of starting the process of digging out all those damned Grey cancer bombs that those vicious little would-be slavemongers implanted in us to make us all obedient little servants. That makes the Mold the single most valuable thing on the planet; it also makes it an invaluable key for winning certain concessions. I mean, obviously we’re going to share it with the world, and relatively quickly; but there’s still advantage to be won from being first in line.
So, that’s what’s in the briefcase that’s chained to your hand. You need to get that cross-country, and a team with a sensitive briefcase should still be anonymous enough to avoid notice. On the bright side, this is one time where we’re not going to say ‘Die before surrendering it.’ If they find you and outnumber you, well, it’ll be a good story to laugh over when everybody’s retired and sitting around the pool at the Village.
Of course, if you get jumped by a Grey stay-behind team, then you should die before surrendering it. Or, preferably, kill all the motherless alien monstrosities and their pathetic human bootlickers. But that goes without saying, really.