Sara Cobbler was one of the children taken away by the Black Carriage. Instead of being fanged, she was forced to work in the Fork Factory. While there, she was put in the coffin at least once. She also befriended Janner. She helped him escape the factory, and later lead a rebellion and escaped the factory along with all of the other captured children.
Sara Cobbler was born in Torrborro. She had passed through Glipwood sometime before the series. Janner remembers that sometime before the series, his mother had been crying because Sara had been taken away by the Black Carriage. Whe taken by the Black Carriage most children are taken to Fort Lamendron and then to the Phoob Islands or Castle Throg to be fanged, but some are taken to the Fork Factory to create weapons for the fangs, like Sara was.
During the Wingfeather War, Janner was also taken to the Fork Factory, and he would have been unlikely to have escaped without the help of Sara. After helping free Janner, she was put in the coffin again. Even so, she was determined to lead a rebellion. The first to join her was Borley, a boy from the Linnard Woodlands. She and the other captives discreetly gathered weapons that they were creating. Eventually, they were ready and locked Mobrik and the Overseer in the coffins. She and the other children helped the Kimeran rebels retake Dugtown from the fangs. The children set up an orphanage at an abandoned factory called Thimble Thumb's Threads.
After the Wingfeather War ends, many of the children return to their homes, bu Sara was not one of them. The remaining orphans travel to Anniera, which had just been restored. Sara was very sad and wept about the news of Janner's death, and is adopted by Nia Igiby, Janner's mother. At the end of Book Four, Sara is seen Boarding Hulwen to go on a quest with Kalmar, Leeli, Nia, and Oskar to find the First Well and try to heal Janner.