The writing is definitely strong. I feel like this is pretty playable without many changes, though I'm not super familiar with the system it's written for. I do think some of the stuff before arriving at the tower could have been slimmed down in favor of devoting more to the encounter with Mac Cumhaill and untying the knot, which feels like it ends abruptly.
I would also consider rewriting the final bullet point in the "What the players know" section to state, "The PCs do not have enough food and water to cross the wastes and will have to find food and water as they go" to encourage players to make detours and pit stops along the way.
Those are fairly minor points though. All in all, I think this is a strong submission.