Ashfall is a young adult novel by Mike Mullin, which revolves around the explosion of the Yellowstone Supervolcano, and the attempts of Alex Halprin and Darla Edmunds to survive its aftermath.

When the novel begins, Alex is a typical teenage kid, staying at home for the weekend in Cedar Falls, Iowa, while his mother, father, and sister go to visit his uncle and his family in Warren, Illinois. The supervolcano erupts, blanketing everything with ash. Alex takes refuge with neighbors, and then ultimately decides to set off to find his parents in Warren. He travels through the countryside, coming across an escaped convict named Target. Target attempts to kill Alex with an axe; he narrowly escapes, and tumbles into the barn of the Edmunds, Darla, and her mother, Gloria. They help nurse him back to health, and he assists them with their farm chores.

Target and a friend brutally rape and murder Mrs. Edmund, while Alex helps to defend Darla. Target's friend is killed by Alex, and when Target comes back, Alex kills him as well. He and Darla then head out across country to go to Alex's uncle's farm. They scavenge for food as they go, and sleep where they can, dealing with cold rain, and incredible amounts of snow. They are scooped up into a refugee camp that is overcrowded and starved, and escape to the uncle's farm. There, Darla and Alex discover that Alex's parents have been gone for five weeks, looking for him. Alex agrees to stay put, because his uncle and aunt and cousins need him, and because his sister is there as well. Darla helps to revolutionize the farm by creating a grist mill which the family can use to its advantage in terms of collecting food as payment, and offering the locals a service. When Alex's uncle breaks his leg, Doc McCarthy sets the fracture and accepts kale as payment. They set up a future trading market, where kale will be traded for pork from the town of Warren, through the doctor. From the farm, Alex and Darla look forward to an uncertain future.