Three-quarters of the way through the novel I’ve always thought is Camus’ finest, its two main protagonists go for a swim after dark in the waters beyond the harbour of their coastal city, which is in the grip of bubonic plague. The city is Oran, in north-west Algeria; the date is sometime in the 1940s. The plague, which gives the novel its name, has sealed Oran off from the outside world. The Mediterranean water into which the men plunge breathes like a fur-covered animal, Camus tells us.