While busking at Union Station in Washington, D.C., world-class violinist Evelyne Weiss is approached by a filthy, homeless, possibly insane man she had known when they were youths. The man warns her of a strange cosmic entity that lives underground, beneath the Potomac River, and begs for her help in playing the bizarre Eldritch Sonata, which is the only thing preventing the One Under the Potomac from waking up and wiping out all of humanity.
The Eldritch Sonata is an original short story inspired by "The Music of Erich Zann".