What does wilson tell tom when they stop for gas?

they fear for their lives

the symbol of the grandfather's heritage in this excerpt from "the medicine bag,” is the beaded bolo tie.

a bolo tie is a cord fastened around the neck with an ornamental clasp which is worn as a necktie. they have been used by native american tribes such as hopi, navajo, zuni, and puebloans since the mid-20th century.

therefore, the fact that the grandfather is wearing a bolo tie refers to his heritage as native american.