"Mallon the Guru" by Peter Straub - In Stories, Edited by Neil Gaiman and Al Sarrantonio, Harper Perennial

Straub shows he is a master of horror in the simplicity of a tale.  He tells the story of a man who seeks enlightenment by visiting a guru in India with a German friend.  As he reaches the village where the guru lives, he is asked to touch a dying boy, who immediately becomes better.  Then he touches a wall which glows neon where his fingers trail.  But the guru does not tell him what he expects.