A more thorough explanation:

Definition: Nova Causa Interveniens refers to an event that comes between the initial event in a sequence and the end result, thereby altering the natural course of events that might have connected a wrongful act to an injury. If the intervening cause is strong enough to relieve the wrongdoer of any liability, it becomes a superseding cause.

Example: A driver hits a pedestrian who is crossing the road. The pedestrian is taken to the hospital and is being treated for his injuries. However, while in the hospital, the pedestrian falls from his bed and suffers further injuries. The fall is a nova causa interveniens because it came between the initial event (the driver hitting the pedestrian) and the end result (the pedestrian's injuries). If the fall was strong enough to relieve the driver of any liability, it would become a superseding cause.

This example illustrates how a nova causa interveniens can alter the natural course of events and affect liability in a legal case.