ToME: the Tales of Maj'Eyal

I could find no way to progress beyond the third level of the halfling complex. Autoexplore just took me to the stairs up and declared there was nothing left to explore. I even tried digging around with the Tooth and using Precognition's vision effect. I suspect the stairs down were destroyed by a falling meteor, as a meteor did hit where I'd thought I'd seen the exit.