Roots: Blade Runner. There are references to Star Trek: The Next Generation, Frankenstein, Dr Jekyll & Mr Hyde, Lara Croft, and 2001. Fitz impersonates Sean Connery.
Continuity: Ceres Alpha has six continents. The Doctor speculates that, at some point in the past, Ceres Alpha suffered a catastrophe, which killed its powerfully telepathic inhabitants. Their life force survived, joining with their world's biosphere to form a single sentient entity. This entity permeates the entire planet. Danyal Bain's archaeological excavations disturbed this dormant psychic force, and the planet began rejecting the effects of the terraforming. At the time of Bain's discovery, the awakened force took possession of twelve embryos in their mothers' wombs, creating a hybrid species to act as emissaries. The entity, and the emissaries, is very powerful; in addition to transforming the terraformed rhizosphere, including microbial life, back to its original state, it can possess a horde of rats, cause widespread computer breakdowns in the city machine, and steal memories. The emissaries are telepathic, and also telekinetic, able to jam the firing mechanisms of guns and cause them to explode. They can be regenerated by contact with the planet's soil, and start to die when cut off from the planet, for example within the TARDIS.
The Doctor's pockets contain a bag of jelly babies, a yo-yo, a monocle and an impossibly long ruler, again suggesting that they are dimensionally transcendental. In addition to his cardiovascular system, his metabolism, tissue composition and antigen profiles are different from those of humans. His eyes appear to be a mixture of green and blue. He impersonates Dr Domecq for a while, in order to investigate the children. He tends to work in metric measurements. He manages to fly the chopper after seeing Captain Foley pilot it.
Anji is killed by Tyran, but resuscitated. The Doctor speculates that the psychic blast from Ceres Alpha affects her latent telepathic centres because the newly born emissaries need a mother figure and she is the most suitable on board, although he notes that this is pure speculation. She used to baby-sit Rezaul, and vividly remembers that first time that she held him, but has never seriously considered motherhood (see Eater of Wasps). Her family owns a shop. She once worked with a trader who used Eastern visualization methods for dealing with stress, and she carries a torch in her handbag. She has a phobia of rats.
The TARDIS toolkit includes a sonic wrench. It still has a fault locator, although this is faulty (as a result of the telepathic signal from Ceres Alpha), and has an artron conduit and phase modulators. It contains antigrav showers. Its telepathic circuits leave it vulnerable to the massive psychic blast from Ceres Alpha, which badly damages it and forces it to crash. Its keys are again isomorphic.
Paxx-Sinopli syndrome is a parasitic disease caused by a virus. It resides in the mid-brain, uses synaptic bursts to energise itself and devours the cerebral cortex. This results in partial paralysis and eventually the victim dies of cerebral emaciation.
At some point, WorldCorp had suspected involvement in a conspiracy to cover up archaeological findings on the planet Reevis. The city machines' terraforming process involves feeding indigenous microbial life to the genetically modified human organisms, and chemical changes are made to the soil, recombining molecules to create soil ideal for the growth of human crops. The City Machine contains spiders and rats, both stowaways from Earth.
Links: Understandably, Dave is still very much on Anji's mind (Escape Velocity).
Location: Ceres Alpha, 11th September 2847, and from 6th November 2847.
Future History: By 2847, Ceres Alpha is the closet planet ever found to Earth's conditions. Unusually, humans can breathe the atmosphere unaided. Earth is over-crowded and polluted, and birds and grass are extinct there. Synthogens have replaced the need for real animal meat (c.f. Original Sin). Corporations such as WorldCorp and PlanetScape terraform new planets to make them suitable for colonization. Humans use devices called accelerators to heal wounds, resuscitate the recently deceased, and make extensive cosmetic changes to their bodies [an early version of body-beppling from Original Sin]; as a consequence, their life spans have increased dramatically, apparently almost doubling in length. Entertainment in the twenty-ninth century includes The Edgar Bergen and Charlie McCarthy Show. Mind probes have been illegal for three hundred years and their use is the only crime still to carry the death penalty in all of the seven worlds [major Earth colonies].
Some years earlier, PlanetScape tried to terraform Gildus Prime, a lifeless rock neighbouring a hazardous spatial anomaly that appeared and disappeared sporadically. The attempt went drastically wrong thanks to the anomaly, resulting in numerous casualties and the planet was abandoned. There were several deaths and the crops withered suddenly over a three-day period. A remote controlled computer base was set up and the anomaly used for breaking into the ether net.
The Bottom Line: Gripping Blade Runner style thriller populated with well-rounded characters and a truly sick villain in the form of Tyran.