Zoe Heriot

Zoe Heriot (surname sometimes spelled "Herriot") was a young scientist from the 21st century who accompanied the Second Doctor and Jamie McCrimmon in their travels aboard the Doctor's TARDIS.

Meeting the Doctor
Zoe was an astrometricist, first class, and astrophysicist on board Space Station W3 (aka The Wheel) when she met the Doctor and Jamie. She introduced herself to them as 'astrophysicist, pure mathematics major', to which her colleague, Dr Gemma Corwyn, added 'with honours'. Zoe had a photographic memory, and was described by her colleagues as 'the librarian'. She was very bad at history, however, as evidenced by her lack of knowledge of the Daleks, the Ice Warriors and the T-Mat fiasco. (DW: The Wheel in Space, The Seeds of Death, The Stolen Earth) Having been taught only the value of logic, her training left her emotionally underdeveloped. This lack of balance led to conflict. Some of her colleagues challenged her about her apparent lack of personal interest in the Wheel when it was about to be struck by meteorites. When she met the Doctor, Zoe was presented with a case study in how illogical, intuitive actions and instinct could be successful.

As Zoe became aware that there was more to knowledge than mere facts, she decided to hide in the TARDIS. She realised that she had learnt as much as she could on the Wheel, where her abilities and role were compartmentalised and defined. Zoe was ready to discover the universe, and her place in it.

Before he felt ready to have her brave the terrors of the universe, however, the Doctor showed her a thought projection of his most recent encounter with the Daleks. (DW: The Wheel in Space)

Travels with the Doctor
When visiting the War Museum on Dulkis, Zoe was reminded of 'the old atom test islands on earth'. At the same time, she was dismissive of the Quarks, claiming 'they're only Robots' (DW: The Dominators)

In the White Void, Zoe was lured out of the TARDIS by seeing her home city on the TARDIS scanner screen. Having recognised the Karkus from the Hourly Telepress of the year 2000, Zoe was able to defeat him in unarmed combat and secure his loyalty. (DW: The Mind Robber) She used her programming skills to solve problems. Whilst helping the Doctor and Jamie deal with the Cybermen's attempted invasion of Earth, Zoe destroyed the computer in the reception at International Electromatics. Determined to not be beaten by a 'stupid tin box', Zoe gave the computer an insoluble program in ALGOL, and delighted in the computer's destruction. With her logic and mathematics, Zoe computed the attack pattern for missiles to set up a chain reaction to destroy the incoming Cyberships (DW: The Invasion). Zoe's great knowledge and intellect were always evident, but never more so than when she was tested on the teaching machines used by the Krotons to teach and indoctrinate the Gonds. Having scored more than double the score of the best Gond students, Zoe declared that the Doctor could certainly answer the questions too (DW: The Krotons). Again using her computational and logic skills, Zoe, in further travels, worked out the trajectory of beacon segments to deduce that a band of space pirates must have their base on the planet Ta. (DW: The Space Pirates)

Eventually the Time Lords sent Zoe back to the Wheel. Having had her memory of her time with the Doctor and Jamie other than her initial adventure with them on the Wheel, removed, she was never aware that she had ever been away (DW: The War Games)

Life after the Doctor
As the years passed, Zoe began to have detailed dreams of her adventures with the Doctor and Jamie. Unable to clearly remember her dreams or reconcile them with the knowledge that she had parted company with the Doctor when the TARDIS left the Wheel, she began to receive psychiatric counseling. (CC: Fear of the Daleks)

When the Doctor was sent to the Death Zone on Gallifrey, Zoe and Jamie seemed to show up and warn him against going further in the direction he had chosen, but he realized that they were an illusion. This was proved right when she vanished as he figured it all out. (DW: The Five Doctors)

After discovering that she had aged by two years after the only experience with the Doctor and Jamie she could remember, Zoe deduced that she had had more adventures with the Doctor which had been wiped from her memory. About a month after her return to the Wheel, the Wheel was attacked by a Cybership. Due to her slight build, Zoe was judged to be unfit for conversion into a Cyberman, but upon scanning her brain and recognizing her above-average intelligence, the Cybermen decided she would be suitable for conversion into a Cyberplanner. The conversion process caused Zoe's memories of the Doctor to resurface.

It also granted her the opportunity to gain control of the systems of the Cybership. Before the conversion could be completed, Zoe had diverted the ship into the only place she could think of where the Cybermen would be unable to hurt anyone else - the Land of Fiction. Once there, she took control of the Land's damaged computer, bringing the Land of Fiction back to life. She used fictional characters and constructs to fight the Cybermen, but came to the conclusion that she needed the Doctor's help to be victorious over the Cybermen. After unsuccessfully attempting to create an accurate fictional version of the Doctor, she opened a hole in space-time and sent a data-stream which drew the TARDIS into the Land. The TARDIS landed far off course, so Zoe created a fictional version of Jamie to protect the Doctor as she drew him to her control center. With the Doctor's help, she was able to destroy the Cybermen once and for all. As the Doctor returned her to the Wheel, the Time Lords' conditioning of her mind returned, and she lost her memories of him for the last time. (BFA: Legend of the Cybermen)

Personality
Despite knowing very little about the Doctor, she was a loyal companion. She described him as old, clever and kind. (ST: The Five Dimensional Man) Despite her apparent bravery, she was quick to call for assistance if she needed it. (DW: The Seeds of Death)

Behind the scenes

 * Zoe's last name has often been given as Herriot, with two R's. However the original script for The Wheel in Space, her debut story, gives her surname as Heriot, with one R.