The Signalman is an elegy: to human frailty, to mighty, all-consuming storms and all of the 'what ifs' that remain. Based on the Tay Bridge Disaster of 1879, Peter Arnott's historical monologue focuses on ageing signalman Thomas Barclay (a magnificent Tom McGovern) ruminating on chance after forty years of guilt; the stories that the press cling onto because small lives are never big enough to fill column inches, and the chaos that led to an estimated seventy five lives being needlessly lost.

There is a robust physicality to Arnott's words, all in Scots, which are lyrical, bawdy and philosophical, but never performed in an overwrought way. Ken Alexander's flawless direction lets these words build, linger and drop – they come in waves, torrents and finally trickling streams, as Barclay, presenting the trial where he was accused of failure to do anything in flashback, tries to make some kind of sense of the chaos that led to the deaths.

There is a section where he rants like an evangelist, mocking any great ecumenical plans, questioning whether a benign God could allow innocent lives to be taken, and hollow laughter at the 'meenisters', all patrician vowels and self-righteous speeches, who would suggest otherwise.

Barclay – speaking of the force of 'devils' that lifted him up into the air and dropped him, scrabbling in the rain like an animal – isn't just an everyman figure, he's a wounded, fallible boy too. By merely bowing his head, and speaking softly, he's the epitome of vulnerability, now twenty four years old, yet seeming so much younger in front of the ones judging his fate.

Above all, it's Barclay's cognitive dissonance of knowing it was structural damage that caused the fatalities, but blaming himself for simply being there, that most resonates here, as the bell strikes only once.

Oran Mor, until Sat 28 Sep; Traverse Theatre, Edinburgh, Mon 30 Sep–Sat 5 Oct, playpiepint.com