On June 30, 2009, a black Nissan Sentra was found submerged at the Kingston Mills locks on the Rideau Canal with four bodies inside: Zainab Shafia, 19, Sahar Shafia, 17, Geeti Shafia, 13, and Rona Amir Mohammad, 52. The family called Rona the girls' aunt. She was their father's first wife, in a polygamous marriage Canadian immigration knew nothing about.

Within three weeks, Mohammad Shafia, his wife Tooba Yahya, and their 18-year-old son Hamed were charged with four counts of first-degree murder. A jury convicted all three in fifteen hours.

But the murders are not the hardest part of this case. The two years before them are. Teachers knew. Two separate child protection agencies were called. Police interviewed four terrified children on a street corner ten weeks before the drownings. An immigration lawyer was offered $10,000 to make on ...