Hi Robert, I'm not sure what step you might be missing. If you got past the trolls and got the glowing egg, that all sounds well and good. Have you done all of this?
Go forward to the end of the ledge and see a giant waterwheel. Climb down the steps and look at the waterwheel. There's a platform up there. Climb the steps close to the waterwheel. Go forward and see a broken ladder.
See a machine on the right platform. Turn the wheel and see sparks come out from top. Saved game here. Open inventory and place the glowing egg on top of the machine. Now, turn the wheel again and hear musical sound. Remember this sound. See that the powered machine opens up the water flow. The water wheel turns. Stand to left side of the machine and look up at the egg. Take the glowing egg off the machine.
Go down the steps and use the water wheel. See Zoë hold on to one of the waterwheel board to reach the top platform. Go forward and jump across the broken walkway. Go forward and climb the ladder.
If you are still stuck after this, let's wait and see if someone else can figure out how to get you moving on with the game again.