I wonder if these stones (which you can read the details of at Canmore ) have any markings on them. Or perhaps the stone in the story is the nearby Clach A Cholumain. There seem to be plenty of candidates, judging by the photos on Mark Stevens' Flickr pages.
The story is told in Hugh Miller's 'Scenes and Legends of the North of Scotland' (1860). It goes on a bit. But it describes this very strange bit of river, which is in a chasm, but the sound of it gets funneled up. The banks were somewhere where 'no one would choose to walk alone' - but the lady of the house of Balconie used to walk with her maid there. Though the maid thought she was a bit weird to be honest. One night she freaked the girl out by trying to make her go near the edge. 'No nearer, ma'am' squeaked the terrified girl, 'Strange sights have been seen in the gully after nightfall.. I shall swoon with terror and fall over.'
But the lady gets really nasty and shrieks 'Nay wretch there is no escape!' and drags her towards the chasm.. suddenly there's a 'strong masculine voice' and a dark-looking man in green appears, saying 'let me accompany you - your surety must be a willing one'. The maid escapes and the lady lets herself be led miserably to the edge.
"She turned round on reaching the precipice, and, untying from her belt a bunch of household keys, flung them up the bank towards the girl; and then, taking what seemed to be a farewell look of the setting sun.. she disappeared with her companion behind the nearer edge of the gulf. The keys struck, in falling, against a huge granitic boulder, and sinking into it as if it were a mass of melted wax, left an impression which is still pointed out to the curious visitor."
Ten years later a man walked up the stream and found a cave in which he met the lady of Balconie.. but you could read that bit for yourself.