She observes. She records. Leave nothing but footprints, take nothing but photographs, she read somewhere, but she walks along undentable concrete paths and her shoes are always clean.
It's harder than it used to be. Sometimes she plays with the idea that the history of the world is the history of increasing irrevocability—jars lids with metal bubbles that pop up as soon as the seal's broken, aspirin in boxes desperately shrink-wrapped for safety, tissues that crumple into ruin after a single use. More and more shops disappear behind signs that say smile, you're being watched. Even in the streets without cameras, people ask questions: how've you been today? Have you tried our new pumpkin-seed bread? What do you think of this weather then?
She responds by choosing her groceries carefully, sticking to the range of fresh food, scooping vegetables and grains into unsealed reusable bags. Bank statements and bills arrive by email. Digital cameras have helped as well: pictures that can be undone to a blank page without leaving a mark. She leads ants from her kitchen with a trail of crumbs, she poisons her weeds and leaves them dead without disrupting the ground, she blows her nose on a handkerchief and then irons it back to new.
It's getting dark. She looks down the street and watches someone lean over a mobile phone. A car drives past and aims, throwing half a puddle outward onto the footpath, and she takes a photo: the arc of water freezes with a streetlight shining through, poised just before it collapses around the victim. Nobody swerves to spray her. As long as that's true, as long as she watches and keeps out of sight and leaves the world unmarked, then nothing she does is irrevocable.
In Hurtle Square somebody turns around by the flowerbeds. Another photo: a blur of red hair emerging from green, a mermaid. Her hair was that bright once, but it's grey now, and she's glad of the anonymity (wrinkles are different, giveaway residue of past expressions, so she never frowns and rarely smiles and keeps her skin uncreased, like the books she reads without ever cracking their spines).
There's a fence and a churchyard, and rustling, and another photo: an incipient tree, three inches tall, growing in a crack in the wall, tiny leaves weighed down with drops of light-filled water. Another, with the zoom lens: smoke rising from somebody's cigarette. She'll catch a bus later (she doesn't drive any more) and file the pictures when she gets home,and then wipe the memory card.
Her feet are wet, so she steps around a section of dryly verandah-shielded path: not even footprints. She's a ghost, she floats, keeping the world safe through an impermeable layer of glass and anonymity. Another photo: the edge of the parklands, with figures and treetrunks she can barely distinguish from each other. People are sitting together and singing, and she remembers what it felt like to be one of them, and she can't walk any closer, the footpath ends and the grass would bend under her feet.
When she gets to the end she'll undo it all. Past the people bending wet grass, winding music back into their mouths; past the smoke thickening back into the cigarette as raindrops fly skyward. The crack in a wall will close up as she passes, a girl in the park will ratchet anticlockwise, water will arc into its puddle as a car reverses by. She'll follow everything right back to the start, and try again.