As the plot opens in 2276, a number of factors are combining to make a diplomatic visit to the 'mother world' of Earth a necessity. Firstly, the forthcoming 500th anniversary of US Independence, which is bringing in colonists from the entire Solar System, obviously needs a suitable representative from Titan. Secondly, the Makenzie family carry a fatal damaged gene that means any normal continuation of the family line is impossible—so both Duncan and his "father" Colin are clones of his "grandfather" Malcolm. Human cloning is a mature technology but is even at this time ethically controversial. And thirdly, technological advances in spacecraft drive systems — specifically the 'asymptotic drive' which improves the specific impulse and thrust by orders of magnitude — means that Titan's whole economy is under threat as the demand for hydrogen is about to collapse.