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Journey Blue was a lieutenant in the Combined Galactic Resistance, which fought against the Daleks. A pilot, she operated under the call sign Wasp Delta.
She was once saved from a pursuing Dalek spaceship by the Twelfth Doctor when he materialised the TARDIS around her just seconds before the spaceship exploded. He took her back to the Aristotle where she saved his life, by convincing her uncle Morgan Blue that he could be useful.
Together, along with Clara Oswald, and two other soldiers named Ross and Gretchen Carlisle, The Doctor and Journey were shrunk using a molecular nanoscaler. they were them put inside “Rusty”, a Dalek which believed the Dalek themselves should be exterminated, through his eyestalk in an effort to discover how he became good and whether or not he could be repaired to aid in the resistance effort against the Daleks.
When The Doctor fixed a radiation leak inside Rusty’s casing, it reactivated, sent a distress signal to a nearby Dalek ship and began killing the crew of the Aristotle. Rusty was stopped by Blue, The Doctor, and Clara when they managed to restore its memory of witnessing the birth of a star. This reactivated the moral side of Rusty, and caused him to order a retreat in the other Daleks, and begin fighting them. It killed the Daleks onboard the Aristotle and left to continue his efforts against the rest of the Dalek empire.
After returning to their normal sizes, The Doctor and Clara went to leave in the TARDIS where Journey asked The Doctor if she could join him; he gently refused to take her, telling her that although she was most likely very kind and brave he did not want to travel with a soldier. (Into The Dalek)