Leylah Fernandez arrives at National Bank Open after tournament win in Washington

Twenty-month-old Amelia liked to play with zippers. One February morning in 2019, the toddler woke when her mother returned to the bed the two had been sharing in a rented room in a Kitchener, Ont. home. Amelia didn’t have her own crib. It was around 10 a.m. Her mother had just used drugs in the bathroom, and then slipped a baggie with what was left of the blue-coloured substance inside a zipper pocket on the front of her sweater. She thought the opioid in her possession was fentanyl. Later testing determined it was, in fact, carfentanil, a fentanyl cousin 100 times more potent than...