Dark Side of a Mountain is a historical study into the effects of ideology, religion and culture on medical science. Section "The Code" is dedicated to the first public health manual on record: The Book of Leviticus, and to its 12th century annotation by Moses Maimonides. Causal relationship is found between rejection of food laws by early Christians, suppression of certain parts of the Bible by Catholic Church, measures against heretics, and resulting inability of medieval populations to contain plague which ravaged Europe in the 6th and 14th century. Truth table illustrates the causes and essential conditions of the Justinian plague and the 1348 plague. Essential conditions of the Justinian Plague were loss of autonomy, lowering standard of living including hygiene due to the onset feudalism, and strategic dependence of Byzantine Empire on imports of essential commodities from infected regions. The plague of 1348 brought about change of life-science doctrine to a set of religious dogmas. The argument goes that the root cause of the pandemic was a flawed life-science doctrine, which could not be challenged due to ideological and religious terror. Quest for heretics effectively eliminated all people who had the ability to identify correctly the causes of plague and who were able to suggest rational measures against its spread. This is presented in the context of information available at that time on the example of measures against leprosy as described in the Old Testament. Section Medical Oaths presents different concepts in medical ethics around the globe. The meaning of medical oath in ancient Greece was far less symbolic than it is now - it was a legal act. Today, medical profession is subject to regulations, which to a certain degree replace the need for formal recognition of an ethical code. Some ancient oaths paid lot of attention to then common practices of arranged marriages and witchcraft; and almost all banned abortion and euthanasia. Japanese medical ethics gets special attention, due to unique relationship between martial arts and the art of medicine. The oath of the school of Enjuin includes meditation over the link between Bushido Code and Japanese understanding of medical ethics, and brief excursion into Japanese medical research conducted in occupied territories during the WWII. Professional ethics in Imperial Germany was entangled in many social and legal issues, from patient confidentiality to palliative care for the dying. Distinguished German ethicist Albert Moll collected evidence of unethical practices of his colleagues and became one of the most outspoken critics of eugenic sterilization after the introduction of the Nuremberg Laws. Implementation of Nuremberg Laws in Hitler's Germany follows as the darkest period in medical history. The Eugenic Trail deals with the topic of pedigree, hereditary entitlement and inbreeding, and search for the causes of societal evils. Eugenics transformed from science to ideology in the mid-19th and early 20th century; but only in Nazi Germany it took on such a malignant form. There was a fundamental difference between American and European eugenics. Whilst the American version was driven by quest for hereditary causes of crime, harlotry, and pauperism (i.e. The Jukes), the European version, advocated by Francis Galton, was pushing a case for the indispensability of noble families for the well-being of mankind out of fear of spread of French troubles (the Revolution of 1848) to surrounding monarchies. Obsession with purity of bloodline and pedigree manifested itself in all parts of English noble life. Only the Soviet Union rejected eugenics in favor of environmental egalitarianism. The last section, Legacy, explores the political, ideological, and financial incentives in medical research in Nazi Germany, and identifies then medical research and the profession in general as the driving force of Nazi policies.