Year Without Summer? That would be 1816, when the Swiss government declared a national emergency. Lord Byron (28) cannot be held responsible for crop failures and famine across Europe, but he is sowing discord with fine abandon. Here he is in the Villa Diodati, loosely attired, still a little drunk, but game for wordplay with Mary Shelley (19) and her pretty step-sister Claire Clairmont (18). The real fun to be had is that it’s Mary and Claire who out-think the not-so-noble Lord.

This is Brighton’s Cast Iron Theatre, with a Fringe-trimmed version of their 2016 production. Co-founder Andrew Allen wrote and directed Year Without Summer and he delivers a polished, literate script, which looked a pleasure to perform. Certainly his three actors – Morgan Bradbury (Claire), Rhiannon Williams (Mary) and Edward Corbett (Byron) – make it vital. As a drawing-room drama, in a small space and in the round, it has a supple energy and – not easy – a nippy charm.

Byron is busy writing Childe Harold’s Pilgrimage at this time. He says he’s exhausted, signing himself in at a local inn as aged 100; it’s probably a ruse. Verse 9 of Canto 3 of his narrative poem begins, “But who can view the ripened rose, nor seek to wear it?” Not him, that’s for sure. However, he has already “worn” Claire, and Mary he would admire rather than seduce – and anyway, there are ghost stories to be written, which is just as exciting.

Mary Shelley’s Frankenstein is taking shape. “My fear,” remarks Mary, “sits under my skin like electricity”. She has a mesmerising story in mind but as yet it has no voice. There are shudders, not jolts, of recognition.

Frankenstein's wretched and solitary creature, if you remember, would “find a wife for his bosom” – but that’s not the Romantic way. The Romantic way is to flee marriage, attempt ‘free’ love and see where that gets you. Well, for Mary and Claire it looks like a dead end; for Byron it’s still a thrill, but only just.

Yes, it’s an historical vignette – nicely, evidently, composed and occasionally rather mannered: lots of fluttering hands, for example. But its play of ideas is more than engaging. Claire is the awkward, intriguing, presence; at a guess, the audience will not know her, and I for one had never heard of her. The dialogues with Mary may be a touch over-extended and are certainly too polite, but as a vindication of their extraordinary story it is well done.

As an artistic creation, I'd call Year Without Summer lissom. Mary Shelley, of course, went on to make something altogether more bulked-up and sensational.