Plot summary
Kate returns to her hometown to visit her ailing mother Diane Janssen and reconnects with her old boyfriend Tom Brennan. They dig up a time capsule with the toy plane inside and Kate sneaks into her mother's hospital room, who rejects her and calls for help. She and Tom flee, but he is killed by police and she abandons the plane. In the present, Locke shows Jack the hatch, and Walt, somehow aware of it, warns him not to open it. Michael is poisoned as he prepares to launch the raft.
Believing Kate is setting him up to be blamed so she can take his spot, Sawyer reveals her criminal history and she admits she was Mars's prisoner. Jack realizes Sun was accidentally responsible, trying to make Jin ill instead so he would not leave. Walt admits to Michael that he burnt the raft, and Sun and Kate discuss the poisoning, implying that Kate manipulated her to do it.
Credits
Adapted from Wikipedia contributors, Lost season 1. HTML formatting and reference markers removed.