It means when we arrived at the Palace Theatre for a double bill of Parts One and Two, we didn't know what to expect.
The two halves can be viewed on separate occasions, but it's easier to keep the various plot strands in your head if you attend one of the twice-weekly combined performances of the whole show. At almost 5 hours in total, it's quite a marathon and at the end you might feel dazed by the numerous narrative shifts -- as if a Hogwarts students had slipped a Dizziness Draught into your compulsory Butter Beer during the interval.
But there's no doubt The Cursed Child is not only an excellent continuation of J.K. Rowling's popular novels, it is also a bravura piece of theatre. It uses every aspect of stage craft -- from high-tech video to innovative puppetry, rousing dance sequences and old-fashioned magic tricks.
Taking the old adage about smoke and mirrors literally, at one great moment clouds of steam billow out of a young wizard's ears.
But not everything has gone according to plan. Barn owl Sprocket was replaced with a digital equivalent after a live bird failed to return to its handlers and instead flew around the auditorium.
Like a runaway Hogwart's Express, the heart of the play lies in the emotional journey you're taken on by Rowling and her collaborators, director John Tiffany and playwright Jack Thorne.
Neatly emulating The Deathly Hallows' epilogue, it opens with a middle-aged Harry, Ron and Hermione bidding goodbye to their various children at Kings Cross' iconic Platform Nine and Three Quarters, as the next generation set off for their inaugural term at Hogwarts.
Now the Head of Magical Law Enforcement who answers to Hermione's Minister of Magic, Harry (Jamie Parker) is struggling to live up to the legend that was The-Boy-Who-Lived. Cracks are also evident in his relationship with his youngest son, Albus (Sam Clemmett), who resents following in his famous father's footsteps, especially once life at Hogwarts takes an unexpected turn.
Although the elder Potter's name is in the title, this is as much -- if not more -- Albus' story and our sympathies gradually shift from the parent to the child, particularly after Harry has some harsh words to say to his boy.
In one of his early roles, Parker appeared alongside the late Richard Griffiths -- Harry's cinematic Uncle Vernon -- in the original National Theatre 2004 production of The History Boys, which included a season at Wellington's St James Theatre. He brings a simmering angst to the pent-up Harry and is not always easy to empathise with.
As The Cursed Child is following on from Rowling's novels and not specifically the films, the choice of Swaziland-born actress Noma Dumazweni for Hermione instead of an older Emma Watson-lookalike proved controversial.
She tackles what could be a thankless role with a calm grace, as Hermione's youthful studiousness is transformed into a stern officiousness that befits her senior position in the wizarding ranks.
Curiously, while Dumazweni has attracted considerable attention, the fact another black actor, Chris Jarman, takes on the role of Hagrid has passed by without mention.
Rowling has pointed out she never specified Hermione's skin colour, it is a shame as much licence wasn't taken with Ron and Ginny who, although impressively played by Paul Thornley and Poppy Miller, resemble perfect grown-up images of their younger selves. And Alex Price, with his silver hair and pale skin, channels Tom Felton's on-screen version of Harry's long-time foe, Draco Malfoy.
If the older characters are inevitably beholden to their film incarnations, the younger ones have no such burdens.
Indeed, as the story progresses, you can sense a torch being passed on, as Albus and Scorpius (Anthony Boyle), who as Draco's only son also has father issues, rise to the fore. So it's disappointing Ron and Hermione's daughter Rose (Cherrelle Skeete) is somewhat underused.
Simultaneously harking back to the past while looking ahead to the future, there are cameos for several fondly remembered characters, particularly Annabel Baldwin as an incorrigible Moaning Myrtle.
While revealing too much about what unfolds would risk incurring the wraith of the Dementors, it's fair to say you might want to brush up on the events of Harry Potter's fourth adventure, The Goblet of Fire, which starred Twilight's Robert Pattinson as the unfortunate Cedric Diggory.
Like Newt Scamander's Tardis-esque briefcase in Fantastic Beasts And Where to Find Them, The Cursed Child's time-twisting plot owes an obvious debt to Doctor Who.
With the recent announcement of a new booking period that goes until February 2018, you might need a Tardis if not a Time-Turner if you don't want to wait that long to get a seat. Despite reports that Warner Bros is reportedly attempting to persuade Daniel Radcliffe to return to play the erstwhile boy wizard in a big screen adaptation, a film series based around The Cursed Child is still some way off.
But although Rowling has indicated that The Cursed Child is very much Harry's swansong, this is surely not the last we'll see of Albus, Scorpius and Rose.
WIN
Weekend and Hachette have a fabulous prize to give away to two lucky readers. Two readers will each win a copy of Cursed Child -- Parts One & Two and a copy of Fantastic Beasts. To be in the draw to win, go to winwiththeherald.co.nz and enter the keyword ROWLING. Entries close Wednesday, Dec 7 at 11.59pm.
Harry Potter and the Cursed Child - Parts One & Two (Special Rehearsal Edition -- this is the play script and the eighth Harry Potter story) by J.K. Rowling, John Tiffany and Jack Thorne, a new play by Jack Thorne (Hachette, $50). Fantastic Beasts and Where to Find Them: The Original Screenplay (this is the film's script), by J.K. Rowling (Hachette, $50).
