The Doctor travels in his trusty Tardis with three companions in this tale; Bradley, Phillip and Amber. Bradley takes the lead in the early part of the story as we see the Doctor struggling with his confused memories. Phillip seems more understanding, and gradually we see why the third companion Amber is no longer travelling with them.
The Tardis crew react to the events around them - or do they?
There are others in the tale who both shape events and are affected by them. A pivotal role is played by The Covellitor - a Time Lord adjudicator. Along with Chaldar, a fellow Time Lord official they have a role in seeing that the test conditions are observed properly. In order to do that they also have to take part in the test, and so they respectively play a Village Leader and Imberhorne in one of the Doctor's memories.
They are just two of the extended crew of the second Tardis craft - and events ensure they all become involved in a fight for survival...