How was it possible that numerous nineteenth-century readers believed in the authenticity of a made-up sensational story about a mesmerist experiment that supposedly arrested its subject between life and death? By juxtaposing Edgar Allan Poe's "Facts in the Case of M. Valdemar" with Justinus Kerner's medical case history "The Seeress of Prevorst," this essay compares the narrative constructions of verisimilitude in science and fiction. But in exploring the viral dissemination of "Valdemar," I also analyze how nineteenth-century print media produced content and credence by means of reprinting-a circular feedback reminiscent of our current world of social media, where unfounded or disproven stories gain credibility by being circulated, shared, and retweeted. Keywords death, mesmerism, literature and science, "Facts in the Case of M. Valdemar" In1829theGermanphysi cian Justinus Kerner published a medical case histor y titled The Seeress of Prevorst: Revelations on the Inner Life of Man and the Intrusion of the Spirit World upon Our Own. In it, Kerner (1914, 4:58) gives a detailed account of a former female patient capable of seeing into the beyond because she was, for seven years, "arrested by some fixation in the moment of dying between life and death." 1 Margaret Fuller (1983, 124), the American transcendentalist and women's rights advocate, praised the text in a May 9, 1843, letter to Ralph Waldo Emerson as "a really good book," and in March 1845 Harper published an abridged US edition. Shortly thereafter, Edgar Allan Poe transformed Kerner's allegedly authentic documentation of "pure facts" (Kerner 1914, 4:56) into a compellingly morbid literar y stor y. "The Facts in the Case of