After marcy, head up next to about 4 lean-tos. There are also a bunch of nice campsites if your goal is an overnighter.
Take a right at the sign. You'll climb a steady uphill until you get to Avalanche Pass. Go through the pass which is usually covered with fallen trees until you get to the beginning of the Avalanche Lake.
Follow the lake around to the right over boardwalks, ladders and rocks until you get to a T at the end of the lake. Here you can either turn around and head back or follow Calamity Brook Trail
Continuing right will take you next to the shore of Lake Colden. It's not rocky, but there are various steep ascents and descents.
Going left will take you to Mt. Colden