What was Lydia Prout’s “dreadfullest thought”? This microhistory, which examines one of the earliest devotional journals penned by a woman in British North America, uncovers surprising connections between the “unruly passion” of a devoted mother who suffered repeated bereavements during the 1710s and the Satanic fantasies of Salem witchcraft confessors in 1692. An annotated edition of Prout’s journal is reproduced in the essay’s appendix.