Janus is the top-secret project at the heart of the Network's machinations. It is a serum developed initially by Philip Carvel. Its purpose is to sterilize 90-95% of the human population in order to prevent the destruction of the Earth's environment and the descent of humanity into wars over resources. It is split into two parts to avoid detection: a protein called GCHN1, which is added to all industrially farmed corn, and an amino acid put into the vaccine for Russian flu. On their own, the components are harmless, but trigger the effects when brought together.
In the UK Version of Utopia, it is revealed that Janus hijacks the Russian Flu vaccine, meaning the vaccine is rendered useless unless if the person receiving Janus is Romani. Only Roma are protected; an indirect way for Phillip Carvel to protect Jessica Hyde.