Richard Thornburg, having looked into this John McClane dude, has shown up at Holly's house.
He commands the nanny to let him in, threatening to call the INS if she doesn't.
He's a real stand-up guy, Dick Thornburg.
On the roof, John discovers the explosives, wired and ready to go. So that's what Hans was doing upstairs.
He radios Powell immediately to warn him of the double cross, but he's cut off midsentence by Karl's machine-gun barrel poking his cheek.
They tussle. Well, tussle is putting it mildly. It's an all out brawl. A fight to the death.
As they exchange blows, helicopters approach in the distance and Hans tells Holly to "gather [her] flock."
Just then, Holly sees her kids on TV, and Hans figures it out—Holly is John McClane's wife. Game changer.
Hans orders everyone up to the roof (which he intends to blow up with them all on it).
Karl and Hans are still fighting and it's getting ugly.
Meanwhile, Agents Johnson and Johnson are all set with rifles in a helicopter. They approach ready to take out anyone and everyone who gets in their way. They don't seem to care too much about harming innocent civilians…
… who, by the way, are all on the roof by now.
Hans, who's got Holly and is loading up all the bearer bonds, tries to radio McClane to tell him he's got his wife.
But McClane's a little busy battling Karl, who shoots John in the shoulder.
Ah, but a little shoulder wound can't take down John Freaking McClane. While Holly sasses Hans, calling him "nothing but a common thief," her husband defeats Karl by wrapping a chain around his neck and dangling him up against a cinder block wall.
He hauls butt to the roof, where he warns the hostages to get down below again—the roof's gonna blow. Holly's secretary tells him that Hans took Holly to the vault.
As he fires warning shots to get the hostages off the roof, Agents Johnson and Johnson mistake him for a terrorist and shoot at him.
He knows the roof's gonna blow, and he's got no way down. Time to cowboy up.
He wraps a fire hose around his waist, and hurls himself off the roof just as the whole thing blows, taking out Agents Johnson and Johnson and their little helicopter, too.
John's okay, though. He pulled a superhero move, shot out a window, and swung into a lower floor. What can we say? He's John McClane.