The film never resolves itself to whether it is providing the pleasures of the 'solo' prison breakout movie (eg. A Man Escaped [1956]) or the 'group' breakout movie (eg. Le Trou [1960]). Whilst visually quite similar, two subtypes are IMHO almost different genres given their different philosophical implications and that they seem to hit different pleasure points in the brain. (Alas, another film where the sub rosa 'based on a true story' immobilises analysis of how the film might have been different.)
Synopsis: San Francisco Bay, January 18, 1960. Frank Lee Morris is transferred to Alcatraz, a maximum security prison located on a rocky island. Although no one has ever managed to escape from there, Frank and other inmates begin to carefully prepare an escape plan.