Frankenstein and the Zombies

Mary Shelley's novel, "Frankenstein" ends with Victor Frankenstein dying from exposure in the frigid arctic. His creation is left in the frozen wasteland presumably to die also. It survives, however, and makes its way southward, ending in the Caribbean Sea. It drowns when its boat capsizes near a small island. Its body eventually washes up on the beach, where it falls into the hands of a wealthy but eccentric medical doctor who is also a voodoo practitioner. The doctor is reviving corpses to make his own personal army of zombies.
A young man and his fiancee work for the doctor tending his house on the small, isolated island. They discover his illegal activities which places them in great danger.