Disclaimer: I don't own these characters, Joss Whedon and Lucas Arts do. So please don't sue.
How Jenny and Doyle Ended up on Taris
Jenny and Doyle had just accepted an assignment from the PTBs where they have to make sure that the Dark Slayer didn't give into temptation of falling and working with evil rather than sticking to her redemption. You see, neither Doyle nor Jenny were around during the time Faith was evil or awake. Because Jenny was killed by Angelus months before Faith was called and Doyle died months before Faith turned herself in. So neither knew how she was going to take to them.
The two found themselves inside an apartment that they were to stay in until they ran into Faith. They had decided to explore the Upper City of get this a different Planet. Jenny lead Doyle towards a building that seemed rather nice. When they walked in they were met with a healer who's name was Zelka. The healer spoke of some kind of serum that could cure an incurable illness. As the two left they ran into the healer's helper who told them that they should give the serum to Zax if they ever found it.
With that done Doyle decided they should go to the Cantina to look around and try to find out what's going on. They learned about the space battle that was going on overhead along with the falling of escape pods from said battle. The two explored for a couple more days before going back to the Cantina where Doyle got drunk off his ass after only two drinks.
Jenny dragged the Irishman back to the apartment to find two people had taken up residents in it. One was a dark haired young woman while the other was an older dark haired gentleman about her age. The man pointed a couple of blasters at her and her drunken companion as she said, "Well at least we found the person we were looking for." She then dropped Doyle and held up her hands.
The dark haired female tilts her head and asked, “Who are you?”
Jenny regarded the woman for a moment before saying, “I’m Jenny Calendar, and the man on the floor is Francis Doyle and we were sent by TPTBs.”