Surveying more than four decades of debates in Canada’s House of Commons around the turn of the twentieth century, Blood Must Tell shows that biologically determinist race-thinking was never accepted by its elected members as unassailable truth. Although racist ideas were openly and habitually articulated by some of Canada’s leading parliamentarians, it is also true that racial determinists regularly met with forceful opposition from defenders of the ideals of liberal and Christian equality. In fact, it was not unusual to see racist statements challenged on the spot and to hear members call each other out for being intolerant and prejudiced. Political ideas of racial equality and multiculturalism were by no means newly discovered in Canada after World War II. They were already present, and well positioned to become hegemonic in contemporary Canadian political life.