Mitchell was born in Vault 21, where he was known by the nickname “Mole Butt” by the younger residents. He left at some point after it was opened, becoming a traveling doctor to help the people of the wasteland. As Mitchell got older, he returned to New Vegas and married his childhood sweetheart. Some time afterward, he retired to Goodsprings, serving as the town doctor.
His wife died at some point, but he doesn’t dwell on the past. If you have visited Vault 21 and come back to see Mitchell, he will explain that he was going to California with his wife. Due to the weak immune system she had from living in a vault her whole life, she passed in Goodsprings, causing Mitchell to settle down there so he could always remain close to her.
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