What effect does the imagery in this passage most clearly have on the plot? Omar hid in the tall grass behind the fort as he heard his friends searching for him. "Olly olly oxen free!" resounded from just around the corner. He tried to remain silent. The air was hot and sticky. A fly buzzed past his face, but he dared not move in case he gave away his position. The grass itched, and his ankles burned for him to scratch them, but he held himself still, trying to be invisible.