Ali Smith has never been afraid to take cleverness seriously. It is a distinctly European sensibility, yet its fullest vindication came amid the xenophobic pageantry of Brexit. The Seasonal Quartet was the work of an intellectual first responder, urgently cataloguing the treasures of pluralism as the body politic celebrated its sweaty fiesta of insularity. Not many novelists could have pulled that off.

It’s not as if that crisis has passed; it’s just been subsumed by bigger ones, and Smith hasn’t been standing idly by. Gliff is to be followed in 2025 by Glyph, a sister novel that will further explore “how we make meanings and … are made meaningless”. As ever, Smith delights in sportive wordplay, but those obliquely iterating titles belie a frank clarity of purpose. The world is on fire, Ali Smith is here to tell us, and this emergency calls for some urgent semiotics.

It’s no accident that the proposition sounds facetious. Semiotics, the study of signs and their meanings, is exactly the sort of zero-stakes, language-adjacent discipline that writers, by convention, are allowed to be clever about. The Name of the Rose, by trained semiotician Umberto Eco, may have been formidably erudite, but it was also titanically inconsequential. Smith doesn’t have time for any of that. She has a crisis on her hands.

In the Brexit novels, that crisis was necessarily specific, requiring a substrate of contemporary realism. This time, though, Smith grants herself more speculative licence, presenting us with a grim extrapolation of our current trajectory. As Gliff opens, two children huddle before a loading dock at the hotel where their mother works. With them is a man called Leif, who confers with the woman in terse snatches before leading the children away. There are microphones and cameras. It isn’t safe to talk. For now, beyond the sparely dystopian vibes, this is all the exposition we get.

It’s all the children get, too. But like displaced children everywhere, Briar and Rose – see what she did there? – are possessed of a fanatical alertness. Leaving the hotel, they find their bearings using Google Maps, where salience is glowingly monetised and the only landmarks are luxury brands: “Now Gucci. Now Nike.” The very surfaces and textures of this world are encrypted, encoded with the brutish ciphers of money and power. But the signs, if you know how to read them, are everywhere.

Returning home, they find that a bright red line has been painted around their house, demarcating it from its neighbours. For Leif, the meaning of this is immediate and indelible: time to go. But negotiating with rule systems is what children do. Finding a gap in the line, they simply squeeze through.

It is a skill they will come to depend on. Separated from Leif, they find a house to squat in. Rose, the younger of the two, turns inwards, becoming besotted with the horses that graze in a nearby field. She names her favourite Gliff, a Scottish word whose many meanings – among them glance, trace and inkling – take a page and a half to enumerate. Here they do duty as both in-joke (polysemy is a big deal in semiotics) and incantation, as one lost child reconstructs her own oral tradition. When Briar tells her they are abattoir horses, she has no use for the designation. “You are bullying me,” she responds, “with words longer than my life.”

It’s a typically Smithian flourish, half wistful and half chilling, and in that it foreshadows a great deal. Growing anxious, Briar conducts reconnaissance missions, venturing to the corner shop and the train station, thinking to retrace their route. But the ticket machines are for people whose devices let them pass. In Smith’s refinement of the Orwellian vision, no boots are required. There’s just the computer saying “no”, for ever.

A workman with a line-painting machine is accosted by an elderly activist. Briar takes note of the model name, and as the scene unfolds toys with its components, its volatile freight of meanings. Again, that name – the “Supera Bounder” – is a typically Smithian gem, a little prism whose prettily refracted colours belie a totalitarian purity of purpose.

Befriended by Oona, the elderly activist, Briar acquires a kindly instructor in revolutionary praxis. Drawing on Oona’s store of memories, they begin sifting the cultural wreckage and decoding their own past. For the children’s mother, we learn, tried to play both sides, a corporate shill turned whistle-blower. Picking apart the antique metaphor, Briar grasps what their mother didn’t: that the gesture was empty not because it made no difference but because truth-telling itself is now obsolete.

Her choice left the children among the “unverified”, without status in the all-pervasive “system”, but what other choices are there? What modes of resistance are available, when a corporatised state controls the very currency of meaning? When the children are separated, Smith shows us one possibility and summons the ghost of another. Like Smith herself, children are born subversives, possessed of a radical plasticity. If they cannot save the world, they will “solve it by salving it”.

It helps in all of this that Smith’s natural mode of discourse, in the best way, resembles the questing and venturesome learning strategies of children. In semiotics, a sign is said to be overdetermined when it must accommodate many meanings. Smith is alert to such abstruse points, as when Rose objects to the idea that a passport proves she’s her: “We prove a passport’s it.” But the cleverness she celebrates is innate and ordinary. It is human, in other words, and Gliff is the mark of just such a native genius.

• Paraic O’Donnell’s most recent novel is The House on Vesper Sands (W&N). Gliff by Ali Smith is published by Hamish Hamilton (£18.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.