The story centres upon the social interaction of a group of railway passengers who have been stranded at a remote rural station overnight, and are increasingly threatened by a latent external force, with a denouement ending.
The deserted station's atmosphere, combined with hearing the non-stop Bath to Gloucester express using an adjacent curved diversionary main line to by-pass Mangotsfield, which created the illusion of a train approaching, passing through and departing, but not being seen, impressed itself upon Ridley's senses.
He warns them of the supernatural danger of a spectral passenger train, the ghost of one that fatally wrecked in the locality several years before, that sometimes haunts the line at night, bringing death to all who set eyes upon it.
The main body of the play is then taken up with the interaction of the varied assortment of the passengers: strangers thrown randomly together in the odd social intimacy of happenstance that rail travel involves, representing a cross-section of English 1920s society.
Reviewing the premiere in The Manchester Guardian, Ivor Brown wrote, "the gentleman in charge of 'Noises off' becomes at times the protagonist, ... he can make a noise so like a train that he might impose on the station master of a terminus; meanwhile, he can throw in a hurricane, as it were, with the other hand.