In 1980-81, the nursing and medical staff of Toronto's Hospital for Sick Children (HSC) were agonizing over an increased death rate on cardiac wards 4A and 4B and groping for the cause. The key to this diagnostic puzzle appeared to surface when hospital radioimmunoassay tests revealed very high autopsy readings of digoxin on four babies who died during this period, Janice Estrella, Justin Cook, Kevin Pacsai and Allana Miller. Since one nursing team was present during each of these infants' final hours, it was assumed that one or more of the nurses had intentionally poisoned the infants with digoxin. A web of circumstantial evidence entrapped team member Susan Nelles, who was charged with murder.