By traveling on this path he is in fact taking the road of death. Steinbeck describes him as having a black hat that covers his black thatched hair. The shack is described as weathered and very old. It casts a rather large shadow to the North east. The darkness of the shadow symbolizes death in the home.
Direction is used to represent positive or negative effects.
Many people feel this came about because the sun rises in the East. Basically this is because the sun sets in the West. In addition to compass directions, height is also a very popular way of foreshadowing the conclusion of the story. The shadow is heading in the direction North East. This means that evil is winning over goodness.