Thomas puffing through Misty Valley
Misty Valley is a valley on a branchline in the television series. It first appeared in the sixth season episode "The Fogman". Cyril, a resident of the valley, was employed as a fogman until the Fat Controller acquired an electronic foghorn to warn the engines of landslides. The foghorn actually ended up creating one, derailing Thomas and almost destroying Toby after he nearly crashed into Thomas' train, but luckily Cyril had laid some detonators to warn Toby.
It later appeared in the eleventh season episode "Thomas and the Storyteller". Thomas planned to take the storyteller to Misty Valley, which was mentioned to be rumoured to be home to several magical creatures, but ended up having to take a detour to rescue Percy from a flooded river.
Misty Valley also was mentioned in the twelfth season episode "James Works It Out", implying that it is part of a branchline that connects at both ends onto the main line.
According to the seventh season episode "Bad Day at Castle Loch", Castle Loch reside in a part of Misty Valley.