The main issue in this case is whether Derek is liable to compensate Margaret and Nicholas in negligent action under the tort of negligence, since this case is concerned with liability of wrong action and relation to pure economic loss. The plaintiffs (P) are Margaret (P1) and Nicholas (P2), the defendant (D) is Derek.
There are three basic things that Margaret and Nicholas must prove in law in order to win a negligence case: Duty of care, Breach of the duty of care, Reasonably foreseeable damages flowing as a result of the breach of the duty of care.
Margaret will seek damages (i.e. financial compensation for both personal injury (physical harm, pain and suffering, psychological harm) and consequential financial or economic loss.