During her childhood, Meshu was discovered to be a "troublesome mind" and was exiled from Isitra, eventually landing on Sao 533. After a length of time, Meshu was able to establish communication with the locals and became a part of their community.
Then, in 2270, the emergence of Berlis Aknista, another "troublesome mind", caused the USS Enterprise to hunt Meshu down as she was the only other living "troublesome mind" and the Enterprise's crew hoped she would be able to stop him. After Captain Kirk convinced her to help, Meshu was transported to Isitra and Spock helped train her mental defenses. Upon their arrival at Isitra, Spock and Meshu began to isolate Berlis, eventually cutting him off from the entire population, and placing Meshu in charge. Fortunately she was able to pull herself away and was returned to Sao 533 by the Enterprise. (TOS novel: Troublesome Minds)