Huw Edwards and the history detectives discover a lost church, search for the oldest castle gate in Europe and find out how the great engineer Thomas Telford built the highest aqueduct in the UK.

The challenges for Huw Edwards and the history detectives include using flash photography to decipher the writing on a ninth century stone pillar, recreating what an iron age fort would have looked like and uncovering an eighteenth century copper works before it disappears beneath a housing development.

Huw Edwards and the history detectives find out why a Welsh master carpenter carved his tools into the wood of a Tudor house and why the Romans built a theatre for their troops in the Welsh hills. They also discover an outstanding example of Welsh chapel architecture.

Huw Edwards and the history detectives interpret the strange humps and bumps in the Welsh uplands, discover one of the oldest wall paintings in Wales and find out why a chicken shed in mid-Wales has stained glass.

Huw Edwards and the history detectives investigate the case of the disappearing house near Holyhead and how it prepared itself for a German invasion during the war. They also search for a lost castle at Portmeirion.