Misty Valley is a valley between Callan and Callan Castle on the Misty Valley Branch Line 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 causing a landslide and trouble for Thomas and 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 the rumoured home to several magical creatures, but ended up having to take a detour to rescue Percy from a flooded river. Later in the same season, Thomas is seen blowing his new whistle in the valley.