Robert Stroud is a convicted murderer sentenced to life in solitary confinement at Alcatraz Federal Penitentiary. While serving his time, he discovers an injured sparrow in the prison yard and finds solace in nursing the bird back to health. This newfound passion for birds leads him to request books on ornithology, allowing him to learn and gradually transform his cell into a makeshift aviary. Over the years, he begins conducting experiments, developing cures for avian diseases, and even writing a book on bird care.

Stroud's work with birds garners widespread attention, bringing him into contact with various people on the outside, including a relentless prison warden who is unsympathetic to his pursuits. Despite his past and ongoing imprisonment, Stroud's achievements and dedication to bird rehabilitation earn him respect and admiration from the scientific community and the public. His journey raises questions about redemption, the human need for purpose, and whether an individual can truly change.