Misty Valley lies along a branch line, which is often very misty. This is why Cyril, a friendly fog signalman who lives in Misty Valley, earns his keep by putting detonators on the rails to warn the engines of fog and landslides. Thomas enjoys seeing Cyril, and puffing over the blasting caps due to that they make his axles tingle. That evening, the Fat Controller visits the engines at Tidmouth Sheds to tell them that he has acquired an electric foghorn. Once he tries to test it, the ground shakes and the rumble makes a few slates of the sheds' roof fall off. He also says that Cyril will not be needed anymore, and will be given a much needed rest. None of the engines are impressed and Thomas is very disappointed rather than unimpressed to hear this, especially because it sounds very loud and to them, sounds like a tugboat horn.
The foghorn is put on the hillside in Misty Valley, and while Percy is puffing through the valley the following day, the foghorn is sounded, to his displeasure. Ironically, after Percy is out of sight, the vibrations from the foghorn create a landslide, which sweeps onto the track and destroys it in the process. Thomas comes along with a goods train, and because the horn is broken, he has no idea about the landslide until too late by derailing and stranding himself on the landslide. With Toby and Henrietta soon coming along, there is no way of stopping them until Cyril comes to the rescue. He puts down a cap to warn them, stopping Toby before he crashed into Thomas and his wreck just in the nick of time. Once the mess is cleared up and Thomas is safely back on the rails, Cyril is reinstated as Misty Valley's fogman.
In a promotional image, Percy is facing in the same direction as Thomas after rescuing him and also looking annoyed.
This was one of the two sixth series episodes that was dubbed in Croatian.
Goofs
In the close-up of Percy at Misty Valley, the tracks in the background lead to the bushes. In the same shot, a wire can also be seen in Percy's right-front window. He is also not pulling any trucks in the surrounding shots. Finally, you can see where the camera is hooked on to him.
At the beginning of the episode, Thomas' driver has blond hair, though after the crash, he has brown hair.
In the second shot of Thomas puffing through Misty Valley and when Thomas runs over the detonator, Annie is facing the wrong way.
Thomas' eyes are misaligned after he crashes into the rubble, and also when he asks the Fat Controller what Cyril will do.
Throughout the episode, the foghorn is switched on even when it is meant to be off. When the foghorn is first shown, the green light is flashing meaning it is on, but the Fat Controller has not switched it on yet. In a close-up of the Fat Controller switching the foghorn on, the switch is already pointing towards the green light but the red light is still flashing. In another close-up of the foghorn horn blasting in Misty Valley, the red light is flashing even though the switch is pointing to the green one.
In the close-up of James at Tidmouth Sheds, Gordon's tender is loose and a few inches away from his cab.
When Thomas says "Ooh, that made my axles tingle!" his eyes are briefly off-centre from each other.
In the shot of Brendam Docks, Cranky's ladder is on the wrong side.
One of the cattle truck's roof from Thomas' train is damaged.
In the very first shot of Percy puffing through Misty Valley, he has a noticeable wobble.
When Thomas runs over the detonator, Gordon's whistle can be heard.
Quotes
Percy: Oh, bother! That foghorn is so loud it rattles my dome, it doesn't even make my axles tingle.