The Beating of Her Wings (S03E02)

A routine murder inquiry in a curiosity shop reveals a secret underground cell. The murder itself may have links to Long Susan's burgeoning property empire, Obsidian Estates, but Reid is far more concerned as to the identity and whereabouts of that cell's prisoner, a young girl kept there for many years. It is an investigation which is to confront him with both his greatest shame and his greatest hope. (BBC)