Abby ( The Judgement of Isskar ) Abby , also known as Amy on certain periods of her life , was a tracer in human form . She travelled with the Fifth Doctor as his companion during his second search for the Key to Time . Biography . Amy , like her " twin sister " Zara , existed to find the different segments to the Key to Time to stop its decay from when the Doctor had recklessly put it together before . The Fifth Doctor was brought to a rainy planet at the end of time , finding a compass which led him to Amy , then just a few minutes old and not yet having a name . Telling him this was a segment to the Key to Time , she asked if he could help her collect two more segments . She turned the first segment into its original form and put it into a satchel leading to another universe . Arriving on Mars in the distant past , the Doctor decided to name the Tracer " Amy " , thinking she had agreed upon the name . Amy realised the segment of the Key was disguised as a capstone on the pyramid in the town . The Doctor and Amy were arrested and taken to Magistrate Isskar , accused of being thieves by Isskar ' s beadles . They were let go with a warning not to approach the pyramid . Understanding but disobeying the warning , inside the pyramid , the Doctor and Amy met another tracer whom already had one of the segments of the Key in her possession , along her assistant in her quest , Harmonious 14 Zink . The Tracer agreed to the Doctor ' s suggestion of " Zara " , " just to shut you up " . At the top of the pyramid , Zara touched the segment and turned it back into a crystal . This caused a gravity well to appear , causing massive changes to Mars ' environment . Zara left with the segment using Zink ' s time ring . The Doctor , Amy and Zink jumped on board an approaching ship , and the Doctor piloted it to safety . Unable to help the catastrophe inflicted on Mars , the Doctor and Amy left in the TARDIS for their next destination . The Doctor and Amy arrived inside a castle on the ring world of Safeplace about 16 , 000 years later . At a castle there , there was a succession dispute between the Valdigian s , Lady Mesca and Wembik . The Doctor concocted an anti - venom for Mesca , whom Wembik had poison ed because she refused to allow Mesca ' s son to become king . Meanwhile , the Ice Warrior s , led by Isskar , now an Ice Lord , were guided to Safeplace by Zara to find the next segment , and began fighting the Valdigians . When the Ice Warriors were repelled , Amy worked out a compromise between Mesca and Wembik — they agreed to be married to one another , so that no matter whose son became king , he would also be the son of the other one . While the Doctor asked Isskar to speak to him , his men brought Amy outside the castle grounds . Zara spent generations manipulating the Valdigians as well as the Ice Warriors . She realised the castle was the next segment and turned the segment into a crystal , trapping the Doctor , the TARDIS , the Valdigians and Isskar inside . She tried using the power of the segments to take Amy ' s segment from her satchel . Instead , Zara blew up her satchel , and the Safeplace segment ended up in Amy ' s possession ; Amy assumed what happened was the segments " just balanced out " . While Zara left with the time ring , Amy turned the segment back into a castle , allowing the Doctor , the Ice Warriors and the Valdigians to escape ; the Ice Warriors took the TARDIS outside . Amy then turned it back into a crystal and placed it into her satchel . The Ice Warriors took the Doctor and Amy onto Isskar ' s ship to take them a tribunal ; Isskar confiscated the segments and sent the TARDIS overboard while the ship was in hyperspace in the event of the Doctor and Amy ' s escape . Zara , being unable to detect Amy ' s segments , travelled back in time with the time ring , having " wrecked the controls " of the ship . The ship was on a collision course with the red giant , Leboon . Isskar showed Amy her segments , hidden outside time inside a strongbox , which Amy opened . When the last escape pod was taken , leaving the Doctor and Amy behind , the Doctor tried fixing the ship , before the Black Guardian intervened , telling the Doctor that he hoped the Doctor could explain the situation . ( AUDIO : " The Judgement of Isskar " ) Her travels with the Doctor turned her into a human being with a strong sense of right and wrong . She became a very clever and resourceful young woman . She saved the life of Romana II when Zara and the Guardians would have converted her into the final segment of the Key . After the Doctor destroyed the Key , Romana invited Amy to Gallifrey to join the the Academy and become a Time Lord . ( AUDIO : " The Chaos Pool " ) Amy later followed Zara to a place called the Sphere . Zara tried to bring her back to Pargrave , a soldier whom Zara had fallen in love with . She changed her name to Abby to infiltrate the Sphere and find Zara , only to find out a major secret from her sister — Zara had fallen pregnant by a man called Marek . He had become Zara ' s protector . He taught Zara and Abby about the Sphere . Abby and Zara could not teleport out of the Sphere . They used their powers to earn enough money to escape from the Sphere . ( AUDIO : " The Sphere " ) Abby and Zara finally escaped the Sphere , only to find more trouble . They found themselves in a village called Compton in 1912 , surrounded by a mysterious fog . The villagers believed the women had killed their loved ones by making them vanish into thin air . The tracer twins were taken into custody . Abby escaped and found herself slightly outside of the village only a week into the future and the village destroyed . ( AUDIO : " The Fog " ) When they escaped the village , Zara and Abby were captured by Marek , who used time technology to escape the Sphere before it ' s destruction . While in flight , they were captured by Kreekpolt . Kreekpolt wanted to use the twins powers to heal his daughter , who was fatal ill , but they were unable to do so . However , they suggested they go to the Grace , who would have the power to do it . At gunpoint , they were led to the Chaos Pool . When they arrived , the Grace granted the tracer twins immortality , and they could only die when they wanted to . After this , Abby , Zara and Marek departed from the Chaos Pool , hoping to start a new life together , raising the baby after its birth . ( AUDIO : " The End " ) She and Abby changed time to make a city survived being killed , but lost Marek in the process . ( AUDIO : " The Line " ) She the wanted to rescue a crashed ship . After Zara went missing she wanted to sacrifice her life so that the inhabitants of a village she stayed at could escape . ( AUDIO : " The Flood " ) She met with someone who said she was Zara ' s daughter . She was still naive about some parts of sex and asked a lot of awkward questions . ( AUDIO : " The Dark " ) She tried to hook Zara up with Kurt . She later lost her memories . She went after Zara when she went into a burning building . ( AUDIO : " The Edge " ) She went to medieval England and tried to stop a battle . ( AUDIO : " The Battle " ) She wanted to go back to The Archive and talk to Chi about the day of her death . On arrival she was arrested for murder . ( AUDIO : " The Archive " ) She came and saw Brondle and Wing , here she met Marek again . ( AUDIO : " Consequences " )