Where does a story begin and end? Science fiction is enduringly comfortable with non-linear narratives even when the stuff of the story has no whiff of time travel or relative distortions in space; indeed, in the SF of the past ten years it may have been more rare and inventive to present a narrative from a single viewpoint in chronological order. And in the same period we've become accustomed to Big Books, with big characters and big action (and often big spaceships or big cities) spread across huge spans of time and space, usually—in the UK at least—in a single volume too large to be gripped comfortably in one hand.

Elizabeth Bear's Worldwired trilogy (published in the US during the course of 2005 as three volumes: Hammered, Scardown, and Worldwired) tells a lot of stories. Each volume reaches a conclusion—if not a resolution—for at least some of the characters, and can be read as a story in itself; but taken together the books expand to tell a bigger story on a much bigger canvas than seems signalled by the tightly paced action, complex characterisation and relationships, and already full plot of the first volume. It's a story about taking a very worldly conflict—a conflict that has already raged across economic, cultural, and literal battlegrounds—out into space. It's a story about first contact with aliens, about contacts between human cultures that initially seem at least as alien, and about reappraising relationships when the battlegrounds shift. It's a story about national and international politics, and that also means it's about relationships: both the relationships between politicians inside and across state boundaries and their relationships with business, science, military forces, and the people they aspire to represent. But, inevitably, it's also about relationships between people on a much more personal level: families, friendships, romances, sex—and all the ties that they imply of honour, blood, and guilt.

Hammered begins with what seems like a little local difficulty in Hartford, Connecticut, which unites a private investigator, a disenchanted police officer, and a gang leader in trying to discover who is interfering in their world. In another part of the forest, scientists who once created a type of artificial intelligence that got at least one of them locked up are being legally employed to do it again, under carefully controlled conditions. Meanwhile, young adults proficient in a very particular type of computer game are being tested in skills no one on Earth has yet needed to use. All of these people are already connected—even more so than any of them think. And this first volume brings them even closer together in a tense alliance; the novel closes with several of its protagonists poised in space, looking at the Earth and at the spaceship that will take them out into a suddenly expanded universe—and that's a splendid metaphor for the simultaneous experience of the reader, who would be well advised to have both of the next books to hand in preparation for this point. This is not to imply that each separate novel in the trilogy is only a journey to the next, or to the overall conclusion. It does mean, of course, that a review that tries even to sketch the plot of any volume would be spoiling it for everyone else; which provides a good excuse to concentrate on the characters instead.

You have to start with Casey. Jenny Casey, née Genevieve, aka Maker, sometime Master Warrant Officer Casey. A woman with a lot of past, and quite a bit of baggage, and a pretty uncertain future. In science-fictional terms, it's significant that Casey is part cyborg—or, to be less melodramatic, that part of her body has been artificially reconstructed and augmented. In plot terms, she's a fascinating character in all sorts of ways: an ex-soldier of both Francophone and Native Canadian ancestry, with extensive experience and flair as a special forces pilot and extensive experience of drug use to sustain that flair, living in Connecticut where her own government can't find her, and making something of a living as an investigator. Both the world in which she lives and her own life story are carefully and plausibly constructed so that she can act as a nexus for all the interwoven plot strands, with connections to governments, corporations, street gangs, law enforcers, medical establishments, and scientists—and with a family and personal history that haunts her and builds connections of its own. But as a character, what makes her different is that she's had time for all this history and experience to build up: she's a middle-aged woman and, for all her remarkable background, she's made an average mess of her own life.

Matching her on one corner of the canvas is Elspeth Dunsany, another talented and troubled middle-aged woman who's experienced and created both triumph and disaster in her life. From another direction comes Casey's sister Barbara, more sleek, more successful, at least as dangerous, and the key to some of Casey's personal baggage. And if we're talking successful and dangerous we can't discount Alberta Holmes, who's holding more strings than there are characters realising they're being manipulated; Constance Riel, who becomes Canada's Prime Minister at a time when it really matters; or Bobbi Yee, a young, beautiful, and deadly ronin. In these books women get to captain spaceships as well as fly them; lead countries and corporations; kill and manipulate people; and generally be as thoroughly unpleasant as their male counterparts. Fortunately some women and some men choose a better path; and there are a significant host of younger characters, amongst whom the girls are again key players throughout the story, who demonstrate a far more positive hope for the future and a reason to keep working to make it happen.

But I notice all this as a female reader, enjoying the experience of finding so many female characters playing a real part in the action. This isn't to downplay the equally well-drawn variety of male characters who drive at least as much of the action, of whom naming only a few should help to show the broad reach of the story: Gabriel Castaign, Casey's former comrade-in-arms, now a scientist and programmer and a love interest for at least two of the women. Razorface, an African-American crime boss who has a number of interests in common with Casey but doesn't yet know the half of her past. Mitch Kozlowski, a decent cop who bends the rules far enough to pursue his own interests in common with Razorface. Frederick Valens, initially seeming to personify the US military-industrial complex but who is eventually shown as a whole person driven by his private life as much as his career. Xie Min-xue, a Taiwanese pilot who finds that politics may not matter in space but that national governments don't let go so easily as gravity. Richard Feynman, the ghost in the machine: an AI persona who holds the key to much of what may become possible and who helps to determine whose side everyone else is on. Charlie Forster, xenobiologist. Leslie Tjakamarra, xenosemiotician. Jeremy Kirkpatrick, ethnolinguist. And the presence of these scientists hints at one of the ways in which the scope of the story broadens across the trilogy, as human concerns begin to encompass the prospect of making contact with alien ways of approaching the universe.

Yet part of the story always remains firmly grounded on earth and in human concerns, and Elizabeth Bear has plotted the global geopolitics of the next sixty years with considerable depth and aplomb. The scientific and technological advances she posits are not innovative in science fiction: implanted communications interfaces, medical applications of cybertechnology, space elevators, and inter-stellar starships. But her world-building is so plausible that they fit without seeming either hackneyed or fanciful, as likely to feature in our future as the enduringly familiar ways that human societies live their daily lives. I will concede that I initially suspected Bear of being Canadian, since it's so rare for an American author to employ Canadian settings or characters or ascribe a major role in the present or the future to Canada itself. But this one has done it, and along the way has helped to expand my knowledge of how to talk dirty in the French-speaking Canada of the future. And her vision of a world in which the US has over-reached itself and left power blocks of Canada, PanMalaysia, the Latin American Union, and the European Union facing the global ambitions of the PanChinese Alliance makes for a compelling story.

In some ways, even at the conclusion of the final volume, the story doesn't end. Individual characters have lived and died. Continents and empires have risen and fallen, in some cases literally. Horizons have expanded. Relationships from the very personal to the cosmic have developed and changed and settled and moved on. The world has definitely changed, and every character we encounter has changed with it; for some characters there has been a permanent resolution, and others are still standing as the narrative closes. But the well-worn framing device for the story, the "editors' note" that opens each volume, offers hope for the future; some characters, but above all the world they live in and have helped to shape, continue with their story.

Claire Brialey also reviews for Vector and Foundation, was a contributer to Damien Broderick's Earth is But a Star, and co-edits the SF fanzine Banana Wings. She works as a civil servant for the UK Government.