Sperm donors were once described by doctors as the “missing ingredient” for infertile couples. These men become an essential part of someone’s genetic inheritance, but in most cases, they never know who they father.

Myf, Michael, Jeff and Ross are just four of many children who were conceived using anonymous donor sperm in the 1970s, but only later in adulthood suddenly discovered their dads were not their biological fathers. In the search for information that could lead them to their roots, we follow men and women as they meet the doctors responsible for their conception, attempt to trace missing files that could uncover the truth about their donor fathers, undergo DNA tests and even appeal to the public and media in the hope of finding answers to their past. But donor-conceived adults aren’t the only ones searching for answers—we meet the donors and find out more about their motives to donate their sperm, now often facing the consequences of their donation and wanting to know more about their offspring.