While visiting Bremen, the narrator's great-grandfather learns from a high police magistrate the sinister history behind an abandoned luthier's shop marked with red crosses. The shop once belonged to Tobias Guarnerius, a craftsman consumed by an obsession to recreate the incomparable sound of a Stradivarius violin. Convinced that the instrument's secret lay beyond physical materials, Tobias came across a treatise on the transfusion of souls and conceived a monstrous scheme. When his dying mother, Brigitta, drew her final breath, he captured her escaping soul inside a hollow soundpost using an occult apparatus shaded by boards from an exhumed coffin.
The resulting violin produced sounds of such overwhelming pathos and anguish that listeners were moved to tears, feeling as though an agonizing spirit were weeping directly into their nerves. Exhibited at a prestigious musical gathering before a German prince, the instrument captivated the royal dilettante, who purchased it for an exorbitant sum. Tobias, initially dazzled by fame and gold, was soon crushed by guilt after realizing he had sold his mother's soul into unending torment. Terrified further when Brigitta's former lover recognized her lamenting voice in the music, Tobias resolved to repurchase the instrument and release the trapped soul.
He embarked on a desperate pursuit across Europe, chasing the cursed violin from owner to owner, as no player could endure its unbearable nerve strain for more than two weeks. Having exhausted his money, Tobias reached Leipzig and attempted to steal the instrument back from a wealthy bookseller. Betrayed and arrested, he fell critically ill in prison and was moved to a hospital. On his deathbed, as an overly verbose chaplain delayed giving him absolution, Tobias mistook a hospital orderly's distant playing for his mother's cries and died in terror without the sacrament. At that exact instant, the violin's strings snapped in Leipzig, and the soul vanished from the loosened soundpost. In Bremen, the horrified public ransacked Tobias's deserted workshop, leaving behind the dark legends that still haunted the boarded-up premises.