Two-Headed Doctor is a forensic investigation into a single LP: Dr. John, the night tripper's Gris-gris. Though released in 1968 to poor sales and a minimum of critical attention, Gris-gris has accumulated legendary status over subsequent decades for its strangeness, hybridity, and innovative production. It formed the launch pad for Dr. John's image and lengthy career and the ghostly presence of its so-called voodoo atmosphere hovers over numerous cover versions, samples, and re-invocations. Despite the respect given to the record, its making is shrouded in mystery, misunderstandings, and false conclusions. The persona of Dr. John, loosely based on dubious literary accounts of a notorious voodooist and freed slave, a nineteenth-century New Orleans resident known as Doctor John, provided Malcolm "Mac" Rebennack with a lifelong mask through which to transform himself from session musician in order to construct a solo career.

Somewhere between puzzle, experimental rhythm, blues disguised as rock, and elaborate hoax, Gris-gris was a collaborative project between Rebennack and producer/arranger Harold Battiste (at the time musical director for Sonny & Cher). A few brief sessions held at Gold Star Studios in Los Angeles brought together many of New Orleans' finest musicians, including Shirley Goodman, John Boudreaux, Plas Johnson, Jessie Hill, Ernest McLean, and Tami Lynn. Along with their complex histories, the cast of characters implicated in the story includes Ornette Coleman, Lafcadio Hearn, Zora Neale Hurston, Cher, Sonny Bono, Sam Cooke, Ishmael Reed, Black Herman, Prince La La, and many others. The story details in discursive style the historical context of the music, how it came together, its literary sources, production and arrangements, and the nature of the recording studio as dream state, but also examines as a disturbing undercurrent the volatile issue of race in twentieth-century music, the way in which it doomed relationships and ambitious projects, exploited great talents, and distorted the cultural landscape.