The cryptic Kate is not quite the innocent figure she initially seems to be. Although the details of her original crime are unclear, Kate has now admitted to the other survivors that she is a fugitive from justice. Prior to the flight, Kate was involved in an elaborate bank robbery in New Mexico, in which she presented herself to the bank manager as an innocent bystander, while she was actually romantically linked with the bank robbers' supposed leader. Posing as a "Maggie Ryan" applying for a loan, Kate was rounded up by the robbers as one of the hostages.

When another hostage overpowered a robber, Kate grabbed one of their guns, but she immediately claimed not to be able to use it. The lead robber then took Kate into a back room, and after a quick kiss, hit her to continue the ruse. The robber brought in the bank manager and claimed he would kill the seemingly innocent Kate, unless the vault were opened. Thinking he was saving her life, the bank manager complied. In the vault, the robber revealed that Kate had actually planned and organized the whole operation. Appearing intent on shooting the manager, the robber was stopped by Kate, who instead shot the leader in the leg, then forced the manager to open a safety-deposit box. Inside was a single item: a small toy airplane.

Sometime later, Kate turned up in Australia as a fugitive. Using the name Annie and claiming to be Canadian, she arrived at the house of an Outback farmer, who, in exchange for help around his farm, offered her a wage and a home. Months later, in the middle of the night Kate attempted to sneak out of the house. The farmer caught her and insisted he drive her to the train station the next morning.

On the road, their truck was followed by a US Marshal. The farmer had seen Kate's picture on a wanted poster at the post office and turned her in for the cash reward. Kate grabbed the wheel and drove off the road, rolling the truck. Despite being free to escape, Kate pulled the injured farmer away from the wreck, giving the Marshal time to capture her.

On board Flight 815, she was in handcuffs, sitting next to the Marshal. Just prior to the crash, she asked the Marshal a favor, which she later claimed was to make sure the farmer receives the reward for turning her in. As the plane began to break apart, the Marshal was injured. Kate stole the keys to her handcuffs, but made sure to apply the Marshal's oxygen mask before putting on her own.

Although initially claiming that she was from Canada, it is revealed that she actually grew up in Iowa. When she recived a letter that her mother, Diane Jansen, was dying from cancer, Kate took a chance and went home. There she met and reignited the romance with her childhood boyfriend Tom Brennan, now married and a doctor at the hospital. The two dug up a time capsule they had buried 15 years earlier, which revealed a tape recording and a selection of Tom's toys, including the little airplane. Kate also convinced Tom to arrange a visit with her mother, who was being guarded, apparently in case of her daughter's appearance. However, once Kate revealed herself to her mother, Diane began screaming for help, and Kate was forced to flee. She asked Tom for his car keys, but he demanded to go with her, saying that the police would be easy on her if she co-operated. Kate sped through the parking garage, direcly at a police car blockading the entrance, but an officer fired off a few shots as she passed, and then crashed into another car. Kate turned to Tom and saw that he was either dead or unconscious. She runs away, leaving behind Tom's toy plane - which she later retrieves from the safety deposit box during the bank robbery.