The monkey of the title is morphine addiction, and the back it's riding on is Cameron Mitchell's in a portrayal of former welter- and lightweight boxing champ Barney Ross. A flamboyant, high-living character, Ross takes off as a Marine for WW II and is awarded a medal for heroism at
Guadalcanal. He soon contracts malaria, however, and is given morphine to ease the pain. Upon his return home and to the ring, Ross's need for morphine increases, nearly ruining his career and family life. The fighting sequences are especially well staged, as is Ross's four-and-a-half-month
struggle in the US Federal Hospital in Lexington, Kentucky, to shake the monkey.