I had a chance to speak with Retha a bit after she'd performed. Nice chat, both her and her bird, Firewing. The bird had mentioned something in the water, which I later learned through others was traced back to a seed in a vase with a suspicious black substance, likely the source of Cassia's illness since it was in her dressing room. I do prefer to have things like that absolutely confirmed, but time wasn't on anyone's side at a certain point in the evening.

[ He wishes he'd had more time to investigate that particular thread. His ability to discern chemical compositions through taste might have helped a bit in that regard, but then he'd been pulled in other directions. It's also more than possible that if there was poison of any sort and the illness was more magic-induced, the Doctor wouldn't have detected anything at all. ]

Umber had replaced Cassia the night she took ill. Never collected payment for their services, either, and simply vanished.