A boy named Michael and his family have moved into a new house that is very old and falling apart. He and his parents are anxious as his new baby sister was born prematurely and may not live due to a heart condition. When Michael goes into the garage, amid all the boxes, debris and dead insects he finds a strange emaciated man. Michael assumes that he is a homeless person, but decides to look after him and gives him food, though he is crotchety and arthritic, demanding aspirin, Chinese food menu order numbers 27 and 53 and brown ale. Michael hears a story that human shoulder blades are a vestige of angel wings. Meanwhile his friends from school become more and more distant as Michael stops attending school and so spends less time with them. He meets a girl named Mina from across the road and over the course of the story they become very close friends. Mina is home schooled and is interested in nature, birds, drawing and poems by William Blake to which her parents introduced her. She takes care of some baby birds who live in her garden and teaches Michael to hear their tiny sounds. Michael decides to introduce her to the strange old man.

Michael asks about arthritis and how to cure it, talking to doctors and patients in the hospital where his baby sister is being treated. The man whom Michael had moved from the garage- revealing a pair of wings at his shoulders- introduces himself as "Skellig" to Michael and Mina.

Michael's baby sister comes dangerously close to death and must undergo heart surgery. His mother goes to hospital to stay with the baby and, that night, dreams or sees Skellig come in, pick the baby up and hold it high in the air, saving Michael's little sister. He subsequently moves on from the garage after saying goodbye to Michael and Mina, answering their questions about his nature by saying that he is 'something', combining aspects of human, bird, beast and angel.