What present did the children give the Professor in "The Egypt Game"?

The children
gave the Professor the gift of the company of others.  Through his secret and silent observation
of their game, he was inspired to care again about living.

The Professor
explains what the children did for him in the form of a story.  He relates that when he was a
young man teaching at the University, he fell in love with one of his students.  The Professor
himself was always "a very quiet and reserved person", but his vivacious Anne brought
enthusiasm, optimism, and fun into his life.  They were married, and traveled much together, he
doing research and she working with the suffering people of the forgotten places they visited. 
Tragically, in one particularly downtrodden area, there was an uprising, and Anne was
killed.

The Professor returned home alone, with "no desire to
teach".  He moved into Anne's store, but "broke off...the contacts that Anne had made
and let the store become a junk shop".  The Professor says that "the store and (he)
became dusty junkyards, and after a while (he) didn't care".

For
twenty-five years the Professor lived in self-imposed imprisonment, having eliminated contact
and involvement completely from his life.  It wasn't until the children started the Egypt Game
in his backyard that the Professor took an interest in anything, and after he finds the courage
in himself to help April, he discovers the joy of community and renewed interest in his work
(Chapter 23).