When Holden steps off the curb at Fifth Avenue, he fears that he will (a) disappear; (b) be hit by a car; (c) call Jane and ask her to her to go with her.

(a) disappear

Every time I came to the end of a block and stepped off the goddam curb, I had this feeling that I'd never get to the other side of the street. I thought I'd just go down, down, down, and nobody'd ever see me again.