Henrik Ibsen's A Doll's House has probably had audiences wondering since 1879 what happened after Nora walked out that door. Lucas Hnath's follow up supplies a logical and intriguing set of answers, bringing Nora (Rachel Berger) back through the same door 15 years after. She has a problem and husband Torvald (P. J. Williams) has the key.

It's not altogether surprising that Torvald has never gotten around to formalising a divorce. He seems to have been frozen by her departure. Nora, who has thrived as a writer of novels, albeit under a pseudonym, has good reasons for wanting the situation regularised.

When she knocks on the door it is her nanny and her children's nanny Anne Marie (Camilla Blunden) who answers. And it's old Anne Marie who explodes wonderfully over what Nora did. She brought up Nora, then was left to bring up Nora's children.

Daughter Emmy (Lily Constantine) has her own solution to Nora's problem. She's also a touching reminder of how Nora might have thought about marriage before she entered it.

Torvald predictably blunders back through the door, home unexpectedly from work and the arguments are truly on. It would be a shame to divulge more.

There's a gusto and a happy robustness to Carolyn Stacey's production that suits the energy with which Hnath's play tackles the "what ifs" of Nora's return.

Berger's Nora has acquired an assurance in 15 years of absence and she walks around her old home fearlessly, taking in her stride the dark squares on the floor where possessions like her piano used to be. William's Torvald initially quails but later reveals a deal of surprising feeling. Constantine as Emmy, in a magnificent yellow dress (splendid design here by Imogen Keen), creates a superbly confident and poised young woman. But this Emmy is also clearly naive about love, marriage and a woman's economic and social position.

Nora is not naive and Anna Marie isn't either. Blunden relishes the part of the old nanny, who understands only too well what prevented her from raising her own child and sent her off to raise Nora and her children. Her early outbursts of strong language help take the play to a place where a very modern debate about the nature of marriage and the rights of women can take place.

Keen's set contains two towering silhouettes of a man and a woman, and, almost hidden on the side, the famous door. The slightly cartoonish feeling mirrors the boldness of the play's style. There's good support from Gerry Corcoran's occasionally surreal lighting and Kyle Sheedy's decidedly non 19th-century sound.

Ibsen might be the source for A Doll's House Part 2 but this piece clearly reaches for the future of a debate started by a play that had an unusually uncompromising conclusion for its time. Check your knowledge of the original and go and see a great take on what just might have happened next.