Sixteen-year-old Benny Foushee, deemed by his father as going-nowhere-fast, embarks on a trip from North Carolina across the United States with his 84 year old Aunt Lucy, his dog Polar and his 1965 GMC pickup. Benny's quest, a challenge both overwhelming but irresistible, is to deliver Aunt Lucy to the big cactus, the giant saguaro in Arizona that she had dreamed of seeing since her own daddy put images of the American West into her teenage brain. Benny's roadway adventures with Aunt Lucy and her on-again, off-again mind, become intensified when he rescues a beautiful young runaway heiress who calls herself Tennessee, stranded alone beside the road with her father's broken Porsche. The foursome, stuffed in the cab of Benny's old pickup, push onward to the cactus: Aunt Lucy with hopes to bring home a story to overrule her braggart brother, Tendall; and Benny, smitten with first love, fearful he cannot bring home alive the old woman he left with.