Mestral was a crewmember of the D'Vahl, a small Vulcan survey ship that crash-landed in Carbon Creek, Pennsylvania, a mining town, in 1957. Through a game of pool and his confidence in his knowledge of simple geometry, he was pivotal in obtaining currency and, consequently, "cryogenic" (frozen) food for the crew. One job he held while on Earth was that of a coal miner.
Of the three Vulcans, Mestral developed a much stronger fascination for Human culture than T'Mir or Stron. He became romantically involved with Maggie, the owner of a local tavern. On the pretext of leaving the Vulcans' apartment in order to retrieve a phase discriminator, he went to a baseball game with Maggie to watch her son play. It was demonstrated here that he began to pick up Human traits, such as lying, whereas ordinary Vulcans do not lie. He did not have a pessimistic view of Humans like his crewmates did. He saw them as empathetic and compassionate, and having great potential. When miners were trapped during a mining accident, he persuaded T'Mir to let him use a phaser-like particle weapon to free the trapped miners. He became a local hero after this incident. He was so fascinated with Earth that he chose to remain there rather than return to Vulcan with his crewmates when a rescue ship came. Officially, T'Mir and Stron reported that Mestral had perished in the crash of their ship. (ENT: "Carbon Creek")