Fork Left
There is fork in the trail -- about three quarters of the way up. You have to take the left fork (see photo), which is often blocked off by a log. From the fork to the dam, the track is on-and-off rather faint, so be attentive.
[The right fork provides an alternative (but a bit lengthy and not mapped here) opportunity to first loop to the south end of Marlette Lake (joining up with the North Canyon trail from Spooner Lake), then north up the west edge of Marlette to the dam, and then return by our "direct" route.]