What are some challenges Percy faced in chapter 2 of the lighting thief?

In chapter 2 of the Lightening Thief, Percy sees 3 old ladies knitting a sock and one cuts a string looking in his direction which symbolizes Percy's lifeline is in danger. The ladies know he is a demigod in danger, and the mist keeps him from knowing this. The mist conceals magic. Later as the book goes on strange events lead to a realization that he is a demigod.