|The following is based on Fallout Tactics and some details might contradict canon.|
If only First Scientist Napstarsky or Second Scientist Jones had survived instead of me. They might have been able to repair the electro-organic linking terminal, and who knows, they even might have saved Vault 0.”— Cheyenne Mountain terminal entries - Terminal Alpha
Third Scientist Lewis witnessed the attempt of the group of super mutants to storm the Vault and following awakening of Calculator. After First Scientist Napstarsky and Second Scientist Jones had died he tried to repair the electro-organic linking terminal by himself. He left several entries on terminals that can be found in Canyon City and Cheyenne Mountain area.
Lewis is only mentioned in Fallout Tactics.