They move between the ticks of a clock. Bullet-time.

Baseline myelinated A-alpha motor fibres conduct at seventy to one hundred and twenty metres per second. Unmyelinated C-fibres crawl at under two. The variable is insulation: oligodendrocytes and Schwann cells wrap axons so the impulse jumps node to node. The HHDRV genome upregulates oligodendrocyte production until myelination is estimated at roughly three times baseline density across major pathways. Sheaths thicken. Internodal distances are retuned. Sodium-channel density at each node of Ranvier increases, so each jump depolarises faster.

The subjective result is not magic speed. It is a nervous system whose sensory inflow, decision loop, and motor outflow have been shifted into a higher temporal resolution while the world outside has not. A thrown object, a muzzle flash, a flinch, arrive as events with interior duration. The cost is sensory gating. The same upgrade that produces the folklore of impossible reflexes is the upgrade that, under overload, produces the neurological glitches of Part Five.