Doctor Levillier was puzzled at the depth of the horror which beleaguered him.

He remembered once driving a staid, well-behaved horse in a country lane.

The animal ambled forward at a gentle pace, flicking its ears lazily to circumvent the flies, apparently at ease with its driver and with the world.

But suddenly it raised its head, drew the air into its distended nostrils, stopped, quivered in every limb, and then, with a strange cry, bolted like a mad thing.

Far away a travelling menagerie was encamping.