You'll climb the tree to your left, and use it to get over the wall.

As quietly as you can, you steal across the courtyard towards the gnarled tree to your left. The tree's branches are thick enough that they make decent handholds - with any luck, you'll be able to quickly scale up high enough to get over the top of the wall. As you strafe around the pool you keep an eye on the frog, which fortunately still hasn't noticed you. You finally duck behind the tree, resting easy now that you're safe for the moment.

But the hardest part of the task still lies ahead. After taking a moment to compose yourself, you begin carefully climbing up the tree's twisted branches. As you shift your weight down onto the first branch, it creaks ominously and threatens to break off. It's too late to bail at this point, so you keep climbing - doing the best you can to avoid any branches that seem weak. But despite your caution, you step onto a branch that can't handle your weight! It breaks off almost immediately, clattering to the ground below you. It isn't very loud, but it is undoubtedly loud enough.