It is very easy to get polio. Patrick Cockburn was six when he woke up one day in the summer of 1956 with a headache and a sore throat. His parents, Claud and Patricia Cockburn, had recently returned to Ireland, to their house in East Cork, careless of the fact that a polio epidemic had broken out in Cork City. He caught the disease and was taken to the fever hospital where, alone for the first time in his life, he was kept in isolation. The virus attacks the nerves of the brain and the spinal cord leading to paralysis of the muscles.

Patrick could no longer walk. The Broken Boy is at once a memoir of Patrick Cockburn's own experience of polio, a portrait of his parents, both prominent radicals, and the story of the Cork epidemic, the last great polio epidemic in the world, affecting 50,000 people. This terrible disease always behaved strangely, attacking the middle classes rather than the poor, children rather than adults, and striking fear everywhere. In Cork the authorities tried to suppress mention of the epidemic in the press; in the rest of Ireland people from Cork were treated as pariahs.

Believing Patrick was dying because of poor conditions in the hospital Claud Cockburn took him home. At first he could only crawl or move in a wheelchair, but gradually he learned to walk again. In 1957, the vaccine that conquered polio reached Ireland.