[Mother-Soon's Journey]

He can potentially get to the tree without being seen. Approaching from the side or back of the hill the building is set into is the best rout he can see. Once at the building, there's a couple high points where if he jumps he can get his arms over the edge. It's not easy though.

If he can manage that without making too much noise, he'll be on top of the building. Unfortunately, for the same reason he could see the window from the ground, so will he be visible if he goes around to the front side of the tree, which is where the window is. As for the window itself, there is a branch he can step on below it and to the side, but the sill will be just out of his reach. Below, one guard paces slowly back and forth. He isn't specifically looking upward, but Waterstrider will have to be careful.