This was once a very important prehistoric site with several hut circles, cairns and cists in the immediate area. The cairns have been mostly robbed of their stone, probably for the field walls nearby but you can still make out the general shape and see some evidence of the cists now the stone has been removed.
I would suggest parking at Harford Bridge, room for a couple of cars, going through the gate on the North of the bridge and following the river upstream. It can get very muddy and isn't always easy to see but you need to follow the path until you go through a gate in the wall where you need to turn left and follow the path up the side of the wall to the top of the hill.
The cache is a clip lock box and is hidden under a large piece of granite, possibly the biggest in the area, and is under the side nearest Tristis Rock. It is covered with a clump of grass, please recover it as found, thanks.