We know we won’t see them, but we are here for the beavers. After extinction in the UK 400 years ago, and reintroduction in Argyll and other sites from 2009, they were brought to the Cairngorms national park last December. They are settling well, but nocturnal and elusive. It is after 9pm when we drop down a steep bank to a waterway all but hidden in the undergrowth. Giant larches rise above a tangle of rowans, birches, aspens, bird cherries and willows. The spaces below are filled with shrubs, rushes and long grasses, everything growing into and out of one another in wild abandon. Above us, a blackbird shows off his sound effects, a song thrush competes with flutey riffs and the robin’s high ecstasy fizzes into static. In the soundless and secretive flow of the stream, we hear a splash. Too fulsome for a duck, more like a flop and afterwash. Then nothing. We note the signs of beaver: the felled trunks, the orange discs of bare wood where they have cut through, and the strips of pale yellow where the bark is gnawed away. Flattened areas on the banks and channels through the reeds show where they have dragged their fellings. Up close, we can see their bite marks in the stumps and the long shavings scattered around. Sharp and strong as chisels, their teeth have iron in them. We creep out on to a vast fallen larch, its lower branches steeped in the stream. Under it, at the far end, the beavers have stashed a pile of wood; it is different from their lodge round the corner, which is a masterpiece of mud-caked sticks. Staring down into the water, we keep imagining we have seen something. A disturbance here, a ripple there. But it’s only the patterns of flow around dangling leaves, or the circling from an insect’s touch. We crouch, caught in the web of an ancient magic, mesmerised by the breathing of trees and the spell of bird notes, the falling dark. And somehow, in the trance, our eyes are opened. For there, perfectly still below the water’s surface – and the same peaty colour – is a rough texture. At one end, the gleam of an eye, at the other, the unmistakable paddle of a beaver’s tail.