The trail starts at the Parking de Biollay in front of the cemetery of Chamonix and near the Montenvers train station. The trail you need to take can be found at the far eastern end of the parking lot where you will enter the Chemin de la Cascade. Take this road up as its bends in a southern direction and becomes a trail. Follow the trail sign for the Alpage the Blatiere. There will also be a sign here that says whether or not the Alpage is open. Follow the trail up for a long way as its zigzags steeply up the mountain. You will reach a junction where you will turn left and follow the trail sign for Blatiere. You will then reach an opening and eventually the Alpage. From there follow the trail up in a south-eastern direction until you reach the next farmhouse at the Alpage Blatiere Dessus.The trail continues on until it intersects with the Grand Balcon Nord where you will turn right in a south-western direction and follow that trail until you reach the Refuge du Plan de l'Aigulle. There are trail markers pointing to the refuge along the way. From the refuge take the trail going down in a south-western direction. It is a long way down with many switchbacks. The first junction that you will eventually reach will offer you to turn left and down to the Cascade du Dard. If you want to add this to your outing then you could take this path and take the latter part of this trail to get back to Chamonix. If you want to go straight back to Chamonix, then simply stay on the trail and follow the signs for the Grepon Parking. Once you are at Grepon parking you can cross below the main road in the direction of the Aiguille du Midi cable car station. Walk past the big square where the cable car station is and turn right onto Rue du Lyret. At the round about take the first right onto Rue Helbronner. Continue on until you see a small path on your left and a sign for the Montenvers Train Station. Pass the train station and turn right at the train track crossing to be back at your starting point at the Parking de Biollay.