canon!OOM: the finale
When Cosmo comes back to his office, he's greeted with two unconscious lackeys and a few mangled panels of drop ceiling. He'd suspected Marty would get away from that setup somehow, especially after the guards who checked the boiler room came back empty-handed.
(He had been surprised to see Liz, at first, but that turned out to be yet another case of Marty putting his friends in danger.)
He gives himself a few minutes, as the group's undoubtedly found some more trouble to dodge, and gets his handgun before heading for the roof access - he doesn't know what will come of that, but at the very least, he can be threatening. He'd judged the timing well; Marty's just starting to make his way down the fire escape.
"Marty! Will you step away from the ladder?"
Marty sighs, but obliges, and Cosmo takes his aim.
"You will give me the box, right now, or I will kill you, right now."
"No."
It's mostly an empty threat, on Cosmo's part, but that doesn't mean he can't aim to scare.
"Jesus! I thought you couldn't kill your friend, Cos!"
"I missed on purpose! Now give me the box!"
"Take the goddamn thing!" Marty swings his knapsack around and reaches into it. "I don't want it. You win, I lose - that's what you want, isn't it? Say it."
He doesn't, at first, but that seems to be the prerequisite for Marty handing the box over.
"I'm sorry, Cos."
"You could have shared this with me. You could have had the power." And really, that's more important than the box itself. There's a reason Cosmo went to so much trouble to talk the matter over with Marty.
"I don't want it."
"Don't you know the places we could go with this?"
"Yeah, I do. There's nobody there."
"Exactly! The world isn't run by weapons anymore, or energy, or money - it's run by little ones and zeroes, little bits of data. It's all just electrons."
"I don't care." Marty turns toward the fire escape again.
"I don't expect other people to understand this, but I do expect you to understand this! We started this journey together."
"...It wasn't a journey, Cos, it was a prank."
Cosmo sighs. "There's a war out there, old friend - a world war. And it's not about who's got the most bullets, it's about who controls the information. What we see and hear, how we work, what we think - it's all about the information!"
"If I were you, I'd destroy that thing."
Marty starts down the ladder, and Cosmo... almost follows him. He's got the feeling this is the end of an era, almost more so than the mess in college, and he's not sure this is the sort of closure either of them really need.
But saying that outright probably won't work, so he aims the gun again and says, "Don't go." His voice is shaking more than he'd thought it would.
Marty pauses. "You do what you have to do, Cos, but if you want to stop me, you have to pull the trigger. You."
Cosmo can't do it, of course. He lets his old friend - former friend, by now - go, and takes a moment to investigate his prize before going back into the building.
After everything in the last week and a half that's failed to surprise him, he really should have expected Marty to hand him a duplicate answering machine.