.. How do I find Mavis's son?

When you talked to Harriet Sherman --

How can I find out more about the ghost?

-- she gave you an envelope with a letter from Joseph Mitchell (!) and a photo of Mavis and her son. What now?

When you look at the photo, right-click on the son to hear Lauren's comment. Maybe the school on his shirt has some info.

After you talk to Mavis again and learn her son's first name --

How can I find out more about the ghost?

-- go home and look up Columbia University in the phone book, then call and ask for Sam Wilcox.

No luck. Blast! Is he using some other name?

In the notebook, combine "Sam" and "John Durkin" to get "Sam Durkin." Call Columbia and ask for him. Bingo!

To find out what gift he gave his mom, go visit Joseph Mitchell at the New Yorker.

How do I find Joseph Mitchell?