In Prohibition-era Chicago, the Doctor and Ace investigate signs that somebody is inflaming tensions between the city's gangs. A universe away, Benny and her new friend Romana revisit the vampire planet from "State of Decay", where an old evil is reborn.
This novel contains examples of:
- Beethoven Was an Alien Spy: The Doctor works with Al Capone to try and keep the peace among Chicago's gangs. Several famous incidents in Chicago gang history, including the Valentine's Day Massacre, are attributed to alien influence.
- Cross Through: At the end of this novel, several of the characters cross to the Missing Adventure Goth Opera.
- Gangland Drive-By: A passing car rolls down a window and sprays machine gun fire through the windows of a restaurant where a gang boss is eating. Nobody is killed, but that's part of the plan: the idea is to lure the boss and his men out onto the street where a second car can get them more easily.
- Hand Cannon: Dekker the Hardboiled Detective packs a Colt 1911. "Some people say the old 1911 Model Army Colt Automatic is big and clumsy and noisy, and I guess it is. But hit a man anywhere with the slug from a .45 and he'll go down and stay down." This gets a Meaningful Echo near the end when he establishes that even a vampire will be severely inconvenienced.
- Hardboiled Detective: Dekker is a hardboiled detective in the Raymond Chandler vein.
- Inspiration Nod: Dekker is a hardboiled detective and part-time first-person narrator inspired by the works of Raymond Chandler; his opening narration is almost word-for-word the opening narration of Chandler's The Big Sleep.
- Manipulative Bastard: Ancient elemental Agonal surreptitiously nurtures carnage in order to feed on the resultant devastation. His latest target is 1920s Chicago.
- Noir Episode: The Chicago half of the plot.
- Required Spinoff Crossover: As a promotional tie-in the first Missing Adventure, Goth Opera, was a sequel to Blood Harvest, the New Adventure released in the same month. (That is, for the Doctor Goth Opera happened first, but for several other characters who appeared in both books Blood Harvest happened first. Ah, time travel.)
- Self-Deprecation: One character mocks another because he can't come up with a better description for that sound the TARDIS makes than "a wheezing, groaning noise". It's the same description Terrance Dicks always used in the Doctor Who Novelisations he wrote.
- Working the Same Case: The incidents in Chicago and E-Space turn out to be the work of the same antagonist, a trans-dimensional being capable of casually hopping between planets and even universes.