Mary Elizabeth (“Mollie”) Parmelee Ives (1850?–1929) has long been a figure of considerable mystery. As Stuart Feder put it, “She is scarcely mentioned in any of the family materials. . . . If not medically an invalid, strictly speaking, she appears to have been treated as one socially.” Indeed, the evidence that has emerged heretofore suggests, at the very least, some unspecified “difficulty”—either physical or mental—associated with Mollie. However, a previously overlooked document in the Ives Papers appears to identify a precise physiological cause for Mollie's condition. This article surveys the extant materials concerning Mollie, describes her alleged symptoms, and re-examines them in the light of the evidence recently uncovered.