The Lepidopterist's Companion (S05E09)

As Father Brown approaches Kembleford's mobile library, Ada emerges to ask for help. Margaret lies under a pile of books, pinned beneath a metal shelving unit. Father Brown is relieved to find that she's still alive. With Margaret now safe in bed, Mrs. McCarthy insists that she help in the mobile library until Margaret's better. Her husband Graham shows them out through his photography shop, bumping into his scruffy assistant Lewis. Later Lewis tells Father Brown that he has a secret in the confessional, before running out. (iTunes)