Donnie and Violet are Ivy-League college students, and don't have fancy names or costumes or anything. But they do have superpowers and are attempting to track down and stop whoever is trying to steal the university's magic that gave them those superpowers, so they suppose that makes them superheroes.
The duo enter an out-of-the-way lab. They are supposed to meet someone here, a BioSci major named Lester who claims to have information, but it seems they have beaten him here. The only living things in the lab are a drooping ficus plant and a couple of literal lab rats crawling around their cage.
They wait for a while. Donnie leans against a desk and closes his eyes while Violet wanders around, examining the cabinets and such.
Ten minutes later, when Donnie is ready to give up and leave, Violet calls him over. Taped to the screen of a computer is a piece of paper. Donnie gestures and the paper flies to his hand. Violet gives him a look, and he tilts it so they both can look at it.
The paper, a computer printout, reads as such:
"It's a...coded message, I guess," comments Violet.
"Why would he leave this?" asks Donnie, "Was he kidnapped? Taken somewhere?"
Violet rolls her eyes. "I can't imagine he'd have time to print it out," she says. "Still...what does it mean?"
Where is Lester?
"Why are you reading that so hard?" asks Violet.
"Just mentally doing some character counts," answers Donnie. "Even without knowing the word lengths, I don't think this is a straight Caesar cipher."
"Makes sense, with the '3' in there. So you think there's an extra step?"
Violet stares at the message some more, then looks around. "You know..." she comments, "why was it on the computer?"
"What do you mean?
"I mean," Violet continues, "if he wanted us to see it immediately, he could have just taped it to the door or put it on the counter or something. This computer's a little bit out of the way. Maybe there's something more to that..."
"The second part, the part below the line..." Donnie mutters.
"What about it?" Violet asks, peering at the paper again.
"If it's a message, it's a weird one. There are only eight unique letters in it."
"...And if it was meant to be just a second part of the message, there would be no reason to have the line there. So what is it?"
Just copy and pasting the relevant bits from Matt's attempted solution and my comment:
The letters of the second line are U, D, L, R, N, S, E, W. They seem to indicate directions: Up, Down, Left, Right, North, South, East, West. Look at Clue #2 and ask yourself what grid of letters could be related.