Over the course of nearly three hours, Kate Bush's first gig for 35 years variously features dancers in lifejackets attacking the stage with axes and chainsaws; a giant machine that hovers above the auditorium, belching out dry ice and shining spotlights on the audience; giant paper aeroplanes; a surprisingly lengthy rumination on sausages, vast billowing sheets manipulated to represent waves, Bush's 16-year-old son Bertie - clad as a 19th-century artist – telling a wooden mannequin to "piss off" and the singer herself being borne through the audience by dancers clad in costumes based on fish skeletons.

The concert-goer who desires a stripped down rock and roll experience, devoid of theatrical folderol, is thus advised that Before the Dawn is probably not the show for them, but it is perhaps worth noting that even before Bush takes the stage with her dancers and props, a curious sense of unreality hangs over the crowd. It's an atmosphere noticeably different than at any other concert, but then again, this is a gig unlike any other, and not merely because the very idea of Bush returning to live performance was pretty unimaginable 12 months ago.

There have been a lot of improbable returns to the stage by mythic artists over the last few years, from Led Zeppelin to Leonard Cohen, but at least the crowd who bought tickets to see them knew roughly what songs to expect. Tonight, almost uniquely in rock history, the vast majority of the audience has virtually no idea what's going to happen before it does.

The solitary information that has leaked out from rehearsals is that Bush will perform The Ninth Wave, her 1985 song cycle about a woman drowning at sea – which indeed she does, replete with staging of a complexity that hasn't been seen during a rock gig since Pink Floyd's heyday – and that she isn't terribly keen on people filming the show on their phones.

The rest is pure speculation, of varying degrees of madness. A rumour suggests that puppets will be involved, hence the aforementioned mannequin, manipulated by a man in black and regularly hugged by Bush during her performance of another song cycle, A Sky of Honey, from 2005's Aerial.

The satirical website the Daily Mash claimed that, at the gig's conclusion, Bush would "lead the audience out of the venue, along the fairy-tale Hammersmith Flyover and finally to a mountain where they would be sealed inside, listening to Hounds of Love for all eternity".

In fairness, this was no more demented than the thoughts of the august broadsheet rock hack, apparently filing his report direct from the 1870s, who predicted that Bush would not take part in any choreographed routines because dancing in public is "unbecoming for a woman of a certain age".

As it turns out, the august broadsheet rock hack could not have been more wrong: for huge sections of the performance, Bush's movements look heavily choreographed: she moves with a lithe grace, clearly still drawing on the mime training she underwent as a teenager forty years on. Her voice too is in remarkable condition: she's note-perfect throughout.

Backed by a band of musicians capable of navigating the endless twists and turns of her songwriting – from funk to folk to pastoral prog rock - the performances of Running Up That Hill and King of the Mountain sound almost identical to their recorded versions - but letting rip during a version of Top of the City, she sounds flatly incredible.

You suspect that even if she hadn't, the audience would have lapped it up. Audibly delighted to be in the same room as her, they spend the first part of the show clapping everything she does: no gesture is too insignificant to warrant a round of applause. It would be cloying, but for the fact that Bush genuinely gives them something to cheer about.

For someone who's spent the vast majority of her career shunning the stage, she's a hugely engaging live performer, confident enough to shun the hits that made her famous in the first place: she plays nothing from her first four albums.

The staging might look excessive on paper, but onstage it works to astonishing effect, bolstering rather than overwhelming the emotional impact of the songs. The Ninth Wave is disturbing, funny and so immersive that the crowd temporarily forget to applaud everything Bush does. As each scene bleeds into another, they seem genuinely rapt: at the show's interval, people look a little stunned. A Sky of Honey is less obviously dramatic – nothing much happens over the course of its nine tracks – but the live performance underlines how beautiful the actual music is.

Already widely acclaimed as the most influential and respected British female artist of the past 40 years, shrouded in the kind of endlessly intriguing mystique that is almost impossible to conjure in an internet age, Bush theoretically had a lot to lose by returning to the stage. Clearly, given how tightly she has controlled her own career since the early 80s, she would only have bothered because she felt she had something spectacular to offer. She was right: Before The Dawn is another remarkable achievement.