"Different timeline, same answer, never."
—Josie to Avenir, Conclusions Part 3
Josie Trent is a skate-punk-girl and the fire behind the Science Club. She has blue eyes and bright red hair it is not shown but Josie has a sister named Luna. She is driven by intense curiosity, a determination to rebel against authority, and a need to seem independent. Josie transferred to Blake Holsey High after being kicked out of her old boarding school (which she later references to when coming up with a way to empty people out of the school before it disappears. Josie walked into the science club on her first day, and after explaining molecular decomposition, proving that she does know about science.
Josie has never been close to her mother, celestial Trent, whose top-secret job drives a wedge between them, and she hasn't been told much about her father. Because of this, she finds it difficult to let her guard down and to trust people. Despite the distance between them, however, mother and daughter do love each other.
Josie's rebellious nature causes a great deal of trouble; it results in frequent conflict with Principal Durst and puts a strain on her friendship with roommate Corrine Baxter. Coupled with her curiosity, Josie's disregard and distrust for authority spurs her on to get to the bottom of the Blake Holsey mystery. She would sacrifice almost anything to discover what Victor Pearson is really up to. However, Josie generally wishes to do good through her actions, to be a hero and not merely a rebel.
She has a unknown relationship with Lucas Randall She is pulled by the strings of trust and distrust. Since the Brainwaves episode, Josie's relationship with Lucas Randall has become more complicated. While it's clear that she does care for Vaughn at least as a friend, his attempts to sabotage Lucas irk her. Marshall also has a crush on her.
Josie and Vaughn have been part of the strange things happening around Blake Holsey. After Vaughn was caught with her Chi Ball, Vaughn and Josie had exchanged intelligence and then memories. Vaughn gained enhanced intelligence, but returned it back to Josie. Josie gained a number of specific memories from Vaughn, including a repressed one from infancy, when Sarah Lynch gave Vaughn a pendant which Victor was to hold onto until the proper time. The pendant was the key to a holographic message to Vaughn that could only be opened using the biometics of Josie and Vaughn. Josie and Vaughn learned that they have the same DNA helix.
When Josie thought Vaughn went into the wormhole to find his mother, she went after him, but landed in the past, when Blake Holsey High was newly built. She was later rescued by the student Science Club members, but Vaughn was temporarily stranded in 1977. Josie went after him and brought him back to the present. Josie decided to use the wormhole to travel back to the past, before Victor Pearson and Sarah Lynch used the Chi Ball in Pearadyne. Josie took the Chi Ball and returned to the future, hoping something good will come out of it. She was dead wrong. It turned out that Blake Holsey High was abandoned, the students and teachers were gone, and only she was left in this alternate reality of the future of her timeline, observed by the Janitor, and Josie's Clone.
For over a year, Josie was trapped in the alternate world, where she found the pendant that Sarah Pearson left behind in the past. Josie was eventually rescued by her clone, who traded places with her in the universe and told her that Avenir was the enemy of her universe. Josie returned to her world and learned that Avenir, the new headmaster, was her father.
Josie, with the help from her friends, is able to prevent Avenir from taking control of the Chi gong ball and having dominion over space and time. Aparently, Josie is one of many Josie's in many alternate realities who have continually fought the same Avenir. With Sarah Pearson's help, the Josie that we know stops Avenir for all time.
In the end Josie and the gang say goodbye and she looks forward to a future of summer school (since she did not graduate like the others) and catching up with her mom.