In March 2021, the Toronto-based reporter Leyland Cecco heard about a memo sent by New Brunswick health officials that warned about a possible unknown neurological syndrome thought to be affecting about 40 people. Since then the story has taken many twists and turns, most recently with a peer-reviewed study that concludes there is no mystery illness after all. Cecco tells Madeleine Finlay about the devastating symptoms that patients experienced, and why the research is unlikely to resolve the conflict over what has been causing them. Help support our independent journalism at theguardian.com/sciencepod