Molly Notkin spills everything — "That the Daddy, the rotter of…"
—That the Daddy, the rotter of a son, and finally a shock-slowed Madame Psychosis had all run down the stairs after the mother and hit the cellar just as the mother had removed the stopper of a Pyrex flask with an enormous half-eaten-away skull on the side, which along with the flaming scarlet piece of litmus paper afloat inside signified an incredibly low-pH and corrosive type of acid.
Context
The instrument itself: the flask that (per this account) unmade Joelle's face is labeled with "an enormous half-eaten-away skull" — the acid advertising, in eaten bone, what it does to faces. Carlisle reads the label as Yorick's memento mori presiding over the Death-Mother's deformation; recorded as his gloss.