Carmen was captain of an ElleryCorp shipping vessel whose only other passenger was an artificial intelligence named LEO. When the Doctor arrived on their ship, he discovered that ElleryCorp was using Carmen as an guinea pig for a test on human sanity in isolation. LEO tried to kill them both for contaminating the experiment. However, the Doctor stopped LEO and left with Carmen. They had many travels together, including one where she met the Doctor's previous companion Grant Markham in prison. (PROSE: Schrödinger's Botanist)
After many travels together, the Doctor accidentally left Yeh in Alaska 1758. Soon after this Yeh met Compassion, who was also left in Alaska after her companion from the Homeworld had left her. Compassion offered to "give [Yeh] a lift" while she searched for her previous companion. The two traveled together for three years.
During their time together, Yeh persuaded Compassion to meet with the War King. Yeh gathered plenty of knowledge of the War during her travels and wrote that Compassion thought the enemy was just a distraction and the true threat was from "family". Compassion later suggested that the emergence of "House Lucia" would be the indication of the real threat showing itself.
Yeh and Compassion were present at the assassination of R B Nevitz.
One of their most notable misadventures took place in the "frontier of time" between the Great Houses' territory and the posthuman future. There, Compassion became greatly distressed upon finding the remains of the 103-form timeship Percival. She then confronted the War King in the middle of a state dinner. Compassion created a second pact with the War King and the head of House Mirraflex shortly before she stopped travelling with Yeh.
After leaving Compassion and settling down, Yeh wrote her (allegedly fictitious) memoir Fantastical Travels in an Infinite Universe, which she called herself "Yvette Carlton" and Compassion "Laura" in. (PROSE: The Book of the War)
Behind the scenes Edit
Carmen first appeared in Ian McIntire's Doctor Who fanfic short story Schrödinger's Botanist, in the charity anthology Perfect Timing, before reappearing (now accompanying Compassion instead of the Doctor) in the Faction Paradox book The Book of the War.