. >> reporter: this 9-year-old has krohn's disease. >> did you say "wow?" >> yes. >> his eyes got huge. very huge. >> whenever i see a kid smile i know mark's with us and mission accomplished. >> reporter: and what does sue think mark would say about all this? >> he'd be like, yeah, she's doing what i asked her to do and she kept her promise to me. >> merry christmas. >> reporter: from a boy's whose own spirit couldn't be broken, the spirit of christmas lives on. >> merry christmas! >> reporter: kevin tibbles, nbc news, chicago. >>> there's more on the story on our new "making a difference" website. you'll see a link that takes you right there on our website nightly@msnbc.com. >>> for now that's our broadcast for this tuesday night. thank you for being here with us. i'm brian williams. as always, we hope to see you right back here tomorrow evening. good night. -- captions by vitac -- www.vitac.com >>> well, anothno round of wicked weather is working its twayhrough the bay area right now. the rain should pick up in the north bay any mine now and in the next