JK Rowling will be able to breathe a sigh of relief after the first preview of Harry Potter And The Cursed Child was met with "whooping and cheering".
Although the show does not officially open at the Palace Theatre in London until July 30, fans have already had their first look at the latest instalment in the Potter franchise, which picks up the story 19 years after the last novel.
Rowling appeared in a short clip beforehand urging fans to keep plot details under wraps. Audience members were also issued with #KeepTheSecrets badges as a reminder.
But fans and journalists who saw the first instalment of the two-part play made it clear they were spellbound.
Clare Fitzsimons wrote in The Mirror: "Spells and hexes combined with laughs and drama mean Harry Potter And The Cursed Child will be every bit the hit everyone expects."
She added: "Judging by the whooping and cheering, nobody was disappointed."
Fitzsimons said the play will appeal to super-fans and Potter novices alike.
Hannah Furness wrote in the Daily Telegraph: "The storyline, a hymn to friendship and teenage misfits, contains enough twists to please the most knowledgeable of fans, who remained resolutely tight-lipped about the plot as they spilled on to the pavement in raptures afterwards.
"Any fears that the world of Hogwarts on stage would struggle to compete with the multimillion-dollar special effects of film were quickly kicked into touch. Objects seemed to disappear before our eyes and characters appeared as if from nowhere."
She added: "The script, written by Jack Thorne and John Tiffany around an original new story by JK Rowling, is fast moving and, most importantly, funny. But for all the laughs and tricks, this story also promises to be a thriller.
"Has Rowling done it again? The audience was in no doubt."
There was also praise for actors Jamie Parker (Harry Potter), Noma Dumezweni (Hermione Granger) and Paul Thornley (Ron Weasley).
Fans tweeted their agreement.
The script is set to be published as a book on July 31, which is Rowling's and Harry Potter's birthday - allowing fans who cannot afford to see the play, or who missed out on tickets, to find out what happens to Harry and his friends.
The plot for the play reads: "While Harry grapples with a past that refuses to stay where it belongs, his youngest son Albus must struggle with the weight of a family legacy he never wanted.
"As past and present fuse ominously, both father and son learn the uncomfortable truth: sometimes, darkness comes from unexpected places."