Hunter S. Thompson receives a letter from the editor of Running magazine, asking him to cover the 1980 Honolulu Marathon, which the editor says should be "a good chance for a vacation". Hunter asks the illustrator Ralph Steadman to accompany him.
On the flight over, he meets a man named Ackerman, who seems to have connections to the drug trade in Hawaii. Hunter covers the marathon with his characteristic gonzo style, weaving his own experiences into the coverage of the story. After the marathon, Hunter, Ralph and Ralph's family move to a rented beach side "compound" on Hawaii's Kona coast. The weather is miserable and they are trapped indoors, besieged by huge waves.
Ralph and his family, upset about the terrible conditions of their vacation, return to England. Later, Hunter reunites with Ackerman to go fishing. Hunter eventually catches a huge Marlin, which he beats to death with a Samoan war club. The fishing boat returns to the dock, with Hunter screaming triumphantly, "I am Lono!", referring to the ancient Hawaiian god. After this, Hunter ends his story in the City of Refuge, hiding from those he upset with his antics at the docks.
The story frequently breaks away to excerpts from The Last Voyage of Captain James Cook , which tells the story of the man the native Hawaiians thought was the reincarnation of Lono and was eventually killed by them when he overstayed his welcome on the island of Hawaii.