Iolo Williams explores four historic estates in Wales, finding out what special places they are for wildlife. These parks are now open for everyone to enjoy but sometimes the wildlife goes unnoticed. Iolo meets with people who have inside knowledge to share, uses his expertise as a naturalist to track down wildlife and finds elusive night-time creatures. In this third episode, Iolo is exploring an old slate mining family's estate in the Snowdonia National Park. He gets up close and personal with a grass snake, uncovers a rarely seen mammal in the garden and, with help from local experts, uncovers the varied wildlife found in the wild woodlands surrounding the house.