Once the ingredients are ready, they get to be added to the thyme-water. In a particular order, in particular quantities, and each with a phrase in Latin from Alli's spellbook, as corrected per their earlier library adventures. Eventually the potion has turned a deep, deep purple (which is mildly confusing, as nothing that went into it actually was that color). Alli stirs it three times counter clockwise, sighs morosely and sets an alarm. "And now to do that every fifteen minutes for the next six hours."