White Darkness (novel)

"White Darkness" is the fifteenth instalment in the series of New Adventure stories published by Virgin Publishing in the 1990s. The story is set in Haiti, 1915 and features the Seventh Doctor, Ace, and Bernice Summerfield. The book was written by David A. McIntee, who derived much of the story's material from Wade Davis' The Serpent and the Rainbow, a research into the practice of voodoo and zombification in Haiti, and also the Cthulhu mythos created by H.P. Lovecraft. Lovecraft lent his name to one of the principle characters in the story, Dr. Howard Phillips, who at one point presents the Doctor with a copy of the Necronomicon, which was given to him by Aleister Crowley and written in the original Eocene language.

Publisher's Summary
We believe that death should always be part of life. 

The Doctor’s last three visits to the scattered human colonies of the third millennium have not been entirely successful. And now that Ace has rejoined him and Bernice, life on board the TARDIS is getting pretty stressful. The Doctor yearns for a simpler time and place: Earth, the tropics, the early twentieth century.

The TARDIS lands in Haiti in the early years of the First World War. And the Doctor, Bernice and Ace land in a murderous plot involving voodoo, violent death, Zombies and German spies. And perhaps something else -- something far, far worse.

Characters
The Doctor, Ace, Bernice Summerfield, Howard Phillips, Nkome/Mait, Captain Eugene Petion, Leopard Chief, Leutnant Katze, Henri, Kapitan Weber, Carrefour, Vincent, Dumarsais Leclerc, Jean Vilbrun Guillame Sam, Lecomte, Tancred Auguste, Francois Lacombe, Claude, Joseph, Kapitan Reise Heinrich, Professor Victor von Stein, Dr. Ingrid Karnstein, Leutnant Klenze, Colonel LV Mortimer, Admiral Caperton, General Charles Oscar Etienne, Major Paul Richmann, Charvius Dubois, CaptainGlen

Continuity
In "All-Consuming Fire," the Great Old One Mait was trying to release is identified as Cthulhu.