The Judgement of Isskar ( audio story ) Publisher ' s summary . " A new adventure in time and space for the Fifth Doctor and his new companion , Amy , as they search for the Key to Time . " On a planet where Time stands still , the Doctor meets a woman who is just a few minutes old . She is a Tracer , sent into our universe by her makers to locate the six segments of the Key to Time . This being without a name wants the Doctor to be her assistant , but she doesn ' t tell him the whole truth . Not at first . Their first port of call is Mars , where a society that one day will become Ice Warrior s lives in peace and civility . But the Doctor ' s arrival will change all that . The universe is dying , a choice must be made , and the Judgement of Isskar will be declared . The price must be paid - even if it takes centuries . . . Plot . Part one . The TARDIS is drawn to an unnamed planet , where the Fifth Doctor is searching for Peri ( who has already left the TARDIS ) in the rain . Time is frozen by a freshly - created female humanoid , who explains to the Doctor that she has been sent by The Grace to recover three of the six segments of The Key to Time . She requests the Doctor ' s help " as a sort of assistant " , due to the fact that he has experience in such matters and her own naïvety . After a brief period of wariness , he gives her what he believed to be a compass , but turns out to be a segment of the Key to Time . She stores it in a bag , the contents of which are stored in another universe , and agrees a compromise with the Doctor - she will return him to the planet once they have found one more segment . They depart in the TARDIS , with the Doctor suggesting to the tracer a number of names beginning with ' A ' for her to adopt . Arriving on Mars , the Doctor christens his new companion Amy , not entirely to her liking . They encounter a Martian , who despite the Doctor ' s fears has no understanding of the word " warrior " , let alone adopts the title of Ice Warrior . The Doctor and Amy attend a Martian market , which lies beneath an under - construction pyramid . Amy senses that the Key to Time is at the top of the pyramid , when there is a sudden earthquake in which several Martians are killed . The Doctor tends to the wounded , while Amy aids the rescue efforts . The two are then arrested , accused of being thieves , and delivered to a magistrate , whom the Doctor cheerfully engages in conversation . After being warned to stay away from the pyramid , they are freed . When attempting to sneak into the pyramid ' s construction site , amongst further earthquakes , they encounter the thieves for whom they were mistaken - Amy ' s " sister " , another tracer sent to find the other three segments , and her associate Harmonious 14 Zink . As Amy tries to help them escape capture by a Martian guard , Harmonious kills the guard , much to Amy ' s horror . Amy ' s sister recognises the Doctor , who the Grace told them to avoid , and mocks her sister ' s new name . The Doctor quickly christens her Zara , and disposes of Harmonious ' gun . While climbing the pyramid , pursued by another Martian guard , Zara tells Amy that the Doctor will leave her once he finds out that she has lied to him . When they reach the top of the pyramid , the four discover that the segment is decaying , rendering it destructive and highly dangerous . As they are accosted by a guard , the Doctor warns that the destruction of Mars by the segment would pale in comparison to the destruction of the universe which could be caused by the collapsing Key to Time . . . Part two . " to be added "