The Time Lords have brought the Doctor to trial, accusing him of gross interference in the affairs of other planets. If he is found guilty he must forfeit all his remaining regenerations. In the hope of proving his innocence, Melanie Bush, an as-of-yet unmet companion from later in his life, is summoned to the court. Hopefully through her help, the jurors will be reassured in letting the Doctor go free by seeing what good acts he stands to commit as opposed to destructive ones.