Sebastian Barry’s plays tend to deal, as Fintan O’Toole once pointed out, with “history’s leftovers”. Now, in this fascinating speculative piece, he tackles head-on the famous extended visit Hans Christian Andersen paid to Dickens at Gad’s Hill in the summer of 1857. Yet even here you feel that Barry’s real sympathy lies with Catherine, Dickens’ brutally marginalised and soon-to-be-discarded wife.

Barry suggests, in fact, a strange affinity between Andersen, the childless, melancholy Dane, and Catherine who was mother of 10: both outsiders reduced to bit-part players in the drama of Dickens’ life at a time of particular turmoil. Dickens’ friend, Douglas Jerrold, has just died and the novelist throws himself into a benefit performance of The Frozen Deep at which he meets his future partner, Ellen Ternan. But Dickens’ whole family life is in crisis. His dependence on Catherine’s sister, Georgie, is painfully evident. His daughter, Kate, plans to marry against his wishes. And his son, Walter, about to be despatched to military service in India, has got the Irish maid pregnant. All this Andersen, the neglected house-guest, observes with rueful concern.

By mixing fact and fiction, Barry heightens the sense of Dickens’ domestic cruelty: it is striking that the great writer shows more concern for the future of the Irish maid than he does for the jettisoned Catherine. Andersen is also made to appear nicer than he probably was: Kate Dickens described him as “a bony bore who stayed on and on”. Yet Barry captures excellently Dickens’ dynamic restlessness and the sense that his supposedly contented family life was one of his greatest fictions. The play also vividly conveys the cost of being closeted with a creative genius. Catherine, often seen as a dull, child-bearing appendage to Dickens, is here rescued from oblivion and sensitively portrayed by Barry as a loving wife, tender mother and even kindly host to the odd Dane.

The tone of the play is quiet, sad, reflective: something beautifully brought out in Max Stafford-Clark’s Out of Joint production interspersed with familiar folk songs. David Rintoul also admirably suggests that Dickens’ whirlwind energy masks a guilt-ridden unease. Danny Sapani even induces sympathy for Andersen as the observer who sees most of the game. And there is good work from Lorna Stuart, doubling significantly as Dickens’ daughter and future lover, and from Lisa Kerr as the resilient Irish maid. But the play’s abiding image is of Niamh Cusack as Catherine, grieving over her departing son and gazing at her tormented husband with a compassion he has hardly earned. Once again Barry has shown that it is to the defeated and discarded that attention must be paid.