There’s a magic trick that Chuck Katis has: You pick a card at random, memorize it, and shuffle it back into the deck. “Got it?” Katis asks. You nod. Seven of spades.

He presents his arm — not a typical next step in magic. “Squeeze my wrist hard,” he commands. “Think about the number or face of your card.”

After you’ve squeezed for a good 10 seconds, Katis reveals the underside of his wrist, which is bare. He massages the area, and suddenly you see, unmistakably, a seven forming in his skin. How’d he do that?

Katis, a Harvard College freshman by way of Falls Church, Va., has been practicing magic for more than 10 years — about the same amount of time he spent working to become a standout swimmer, earning a spot on Harvard’s swimming and diving team.

As a high school student, Katis founded The Magic of Miracles, a nonprofit that brings magic to young cancer patients, allowing them a much-needed release from their difficult daily lives.

“I was watching ‘House,’ or one of those medical dramas, and the story involved a young child, and I was just playing around with a deck of cards, practicing some stuff, and I realized that I’d been doing magic since I was 8 years old and had been performing for friends and family, but I wasn’t really using it for anything other than entertainment,” said Katis. “So I put the two together and realized that, with everything these kids are going through, they could really use a distraction.”

Katis and his small staff travel to area hospitals to perform, and then teach tricks to the kids “so they can develop and learn their own magic and perform for other patients, nurses, and also themselves, to take their mind off of stuff.” Katis is talking with local hospitals about expanding the Virginia-based organization to Boston.

“Whatever little bit of courage I needed to start something to potentially help a lot of people is nothing compared to the courage these kids have to maintain,” he said.

At Harvard, Katis is also predicted to do great things. He’s currently the Crimson’s top breaststroker and individual medley swimmer, and his coaches believe he has an excellent shot to win the Ivy League Championship in both events and qualify for the NCAA Championships.

But Katis might’ve never made it to Harvard, if not for a little … magic.

While returning from a recruiting trip to Palo Alto, Calif., Katis was deciding between Stanford and Harvard. “I was on one of those jumbo jets, about 500 people, and had no idea where to go. Both schools were great, swimming is great at both schools … so I threw it in the air and said, ‘God, give me a sign,’ and I just let it go,” he recalled.

“I was coming back from the plane’s restroom, and I was wearing a Stanford sweatshirt, and the guy sitting next to me asked if I was a Stanford student. I explained how I was on a recruiting trip, and of all the people on the plane, he said, ‘I was a Harvard undergraduate.’ The ‘Twilight Zone’ theme song started going off in my head.”

Katis’ seatmate was in his late 20s and already a vice president for a renowned media corporation, as well as a former Rhodes Scholar. The decision crystallized for Katis, who is considering an economics concentration.

Katis said he thrives on the “pure competition” of swimming. “Our entire team is going to do great things this year. We’re all very excited,” he said.

And from his Harvard dorm room, he’ll continue helping his foundation raise funds and grow. “To see the reaction of people, to see how people forget about the rules of the world for just a second … every second of that I can give is worth it.”