From the summit of Longs Peak, scramble down the north ridge, following cairns and trails. This is the Old Cables Route aka the North Ridge. You'll eventually find two 70' raps (or a 5.4 downclimb). Walk along Chasm View to just past the Longs/Lady Washington saddle towards "The Camel", a distinct feature on the ridge that resembles a camel. At this point, hop over the ridge and start descending east. You're aiming for a hidden gully that will take you down to just above Chasm Lake. Be careful not to go too high or too low when aiming for the gully. Some good sense and a bit of scrambling will take you to the top of the gully that cuts back south-west. Descend the gully, and make your way back to Chasm Lake. Watch for loose rock.