THE SOURCE

40 cases of severe gastroenteritis hit Villeneuve. The town wants a culprit and has two: Idris, a foreign student (“patient zero”), and the new biotech lab (“a leak”). Public meeting at 6 pm.

The public-health doctor hands you the investigation: “Forget the rumours. Look at who fell ill, and what they had in common. Like John Snow in 1854.”

Four rooms, one investigation: the case map, the incubation, the genetic tree, then the meeting. Each piece goes into your case file.