Episode 1

Iolo Williams tracks Wales' rarest and most elusive mammal, the pine marten, and sees ospreys fishing in the Cambrian Mountains of mid-Wales.

Episode 2

Iolo Williams looks for cuckoos in the Elan Valley, red squirrels genetically unique to the Cambrian Mountains, and golden plover on the hills surrounding Plynlimon.

Episode 3

Iolo Williams tracks goshawks and finds remnants of prey and chicks in a huge nest. He also looks for rare nesting curlew and a stunning day-flying moth called the Welsh clearwing.

Episode 4

In his final trek, Iolo looks for a bird you wouldn't expect to see in Wales as it is meant to be extinct here. But a golden eagle is secretly living in the Cambrian mountains.