Is a plaintiff liable for injuries sustained by a firefighter as a result of negligence?

First, that rule and that exception require the firefighters to have been "summoned" to a fire. "[T]he firefighter's rule involves the question whether a person who negligently has started a fire is liable for an injury sustained by a firefighter who is summoned to fight the fire; the rule provides that the person who started the fire is not liable under such circumstances. (Citations omitted.)" (Knight v. Jewett, supra, 3 Cal.4th at p. 309, fn. 5, 11 Cal.Rptr.2d 2, 834 P.2d 696, italics added.)