The signalman reveals that he is being haunted by a spectre which has appeared at the entrance of the tunnel next to his signal box, and these visions begin to likewise trouble the traveller in his sleep.

SInce airing it has received critical acclaim, being widely regarded as the best episode in the series and one of the greatest works of horror television ever made.

[1][2] A man (referred to as "The Traveller" in the cast list) observes the solitary figure of a signalman standing by the track in a railway cutting.

The Signalman reveals the reason for his initial fear; the Traveller's waving action and words mimic those of a ghostly spectre which rings his bell and is visible beside the red tunnel light.

The Signalman explains that the spectre had returned a week before and has appeared since in fits and starts, always by the light at the tunnel and always gesturing with one arm across its face and the other waved in warning.

The Signalman notes his dilemma; if he was to telegraph "danger" he would not be able to give any reason why and would surely be displaced or fired, so he feels powerless to prevent a possible calamity.

Running towards the scene, he attempts to warn the Signalman, who is standing transfixed on the rail line beside the red light at the tunnel entrance.

Turning around and standing in front of the red light, the driver tells him that he called, "Hallo, Below There, Look Out", with one hand covering his face and the other waving in warning.

In The Signalman, adaptor Andrew Davies adds scenes of the traveller's nightmare-plagued nights at an inn, and re-affirms the ambiguity of the traveller-narrator by restructuring the ending, and by matching his facial features with those of the spectre.

For example, the appearance of the spectre is stressed by the vibrations of a bell in the signalbox, and the recurring red motif connects the signalman's memories of a train crash with the danger light attended by the ghostly figure.

"[2] Dave Rolinson notes that while "the adaptation inevitably misses Dickens' nuanced and often unsettling prose ... it achieves comparably skillful effects through visual language and sound, heightening theme and supernatural mood ...

In 2023 it was remastered in 2k resolution by the BFI and released on Blu-ray alongside The Treasure of Abbot Thomas (1974), The Ash Tree (1975), Stigma, The Ice House, A View from a Hill (2005), and Number 13 (2006) as Ghost Stories for Christmas - Volume 2.

[8] This included Simon Farquhar's essay, the Lawrence Gordon Clark introduction, and a newly-recorded commentary by television historian Jon Dear and writer and actor Mark Gatiss.