LS of the old prison on the Isle of Youth in Cuba, Cuban workers transform the prison into a new institute for Hydraulics and Engineering, during this 1967 communist experiment.  The students study there part time and work to reconstruct the building part time.  The workers integrate military training into every aspet of living on the isle, shots of the military training.  The young people urge other Cubans that a communist revolution is the only way for Cuba.  LS of a large crowd waving a Cuban flag and a communist flag.