Pledged To The Dead — Seabury Quinn

What started as a lighthearted flirtation with a beautiful, strangely dressed maiden under the New Orleans moonlight ended with young Ned Minton pledged to eternal love with a girl who had died a century before -- a promise enforced by the all-too-real fangs of the demon-serpent who guarded her. Ned's only hope is that French physician and occult investigator Jules de Grandin can get to the bottom of it and end the curse that keeps the lovely Julie d'Ayen shackled to the material world -- before the eldritch serpent's fangs end Ned.