Jool arrived on Moya at the end of season 2, as a frozen corpse. The Diagnosan the crew visit in Season Of Death preserves the bodies of many beings who were mere seconds from death. Jool and her cousin were hijacked whilst on a tour, frozen for 22 cycles, and transported across the galaxy to be a donor. Whilst her cousin died when thawed, Jool was able to survive, suggesting that not all of the doctors victims were in the state he suggested.

At first, Jool treats the rest of the crew as scum, appearing to think of herself as near royalty. She constantly criticises others, whilst believing herself elevated. Chiana takes an instant disliking to her, and this is made worse when Jool and D'Argo become close in season 3's quite excellent Revenging Angel. Her most annoying feature though is her scream, so powerful and high pitched that it can melt metal.

Jool takes a step back to being simply human when we find out that Jool wasn't quite honest about how she was captured, and that there had been no tour. However, before truly becoming a proper member of the crew, she decides to leave at the beginning of season 4, to continue her pursuit of history. The opportunity presented in the episode Sacrifice to study an ancient culture means that the crew of Moya continue their journey without her.