Ah. You can use the Teleport gloves to send someone up to the ledge near Mona's tent, then they can lower the ladder there.
I can't believe, in all the play-throughs I've done, I never thought of that. So obvious, but I only ever used it as a way of sneaking out again. Which I did repeatedly without ever seeing "hey, this is also a way in!" D:
Maybe I assumed it would catch the unwanted attention of the nearby guards.
