Park at the Pont du Countet car park.
(S/E) Head towards the bridge and, just before you reach it, take a path on the left (do not cross the bridge). You will come to the Belle et Sébastien shelter.
(1) Continue north and walk up the valley, staying close to the stream.
(2) At marker 413 (top of the circular), cross the river via a small bridge. Descend the valley (south). At the bottom, take the Pont du Countet bridge and you will soon reach the car park (S/E).