The firefighter scooped up the figure slumped on the kitchen floor and dashed for the ambulance waiting on Blake Street. As he moved through the smoky haze, he was struck by a thought that is still with him: It was like nothing was in his arms.

As the ambulance sped toward the hospital, emergency medical technicians administered oxygen; one reflexively commented on the overpowering smell. Right away, as if to apologize, the patient spoke up. It had been more than a year since he had been permitted to shower, he said.

A police officer in the vehicle leaned in.

The patient started speaking and did not stop. He gave his name, said that he was 32 years old and had spent most of his life held captive by his father and stepmother, who locked him in his room for some 23 hours a day.

At the hospital, he continued his story. He had been trapped for two decades, forced to defecate into newspapers and to funnel his urine out the second-story window. He hadn’t seen a doctor or a dentist in 20 years. Sometimes he was fed a sandwich. His teeth were so decayed they often broke when he ate. He was 5-foot-9, but he weighed only 68 pounds.

The ride in the ambulance, he said, was the first time he had been let out of the house since he was 12.

Then, he made a confession. He was the one who set the fire. He used a lighter forgotten in the pocket of an old jacket that his stepmother had given him. If he did not die in the fire, he had reasoned, he might finally be set free.