After a commercial break, we watch Walter lug a sled with equipment wrapped in canvas out to the middle of the lake. "Here. It will do," he says, like WHO ARE YOU TALKING TO, WALTER, and he yanks off the canvas and sets up all his equipment, which includes hoses and tubes and a generator, and a couple of corrugated metal planks that form a kind of V-shaped gateway.
He checks his vial of cure one more time, and then spots Carla standing a little ways away, and he's glad to see that she's changed her mind. Then Nina steps out from behind Carla, because apparently the two of them decided that Carla would just STAND THERE and hope Walter spots her, whereupon Nina could step out from behind her all dramatically. Walter tells Carla that she disappoints him, and tells Nina to go home, because there's work to be done.
Nina urges him not to do it, and he cavalierly tells her he'll be there and back before she knows it. Not the point! She makes the mistake of saying "if William were here," and Walter seizes on that and asks her why William isn't here, and Nina offers up the lame "looking for funding" excuse, and Walter's all, "Oh, he's in Europe chasing funding? Too busy to come and stop me from destroying the universe?" Hee!
The point is, Walter figures (correctly) that Nina's phoned William several times today but William hasn't got back to her. Why? Because William would have applauded what Walter's doing: "You know how many times that William has encouraged me to take this very risk? To expedite our espionage program?" Nina doesn't believe him, which Walter says is because she doesn't understand William: "Like everyone else, you're blinded by the charming manner, the air of intelligence, the whole damn show."