Master Thief is a perk in Fallout, Fallout 2, Fallout 2d20 and Fallout Tactics.
“A Master Thief has a one-time bonus of +10% to the Sneak, Lockpick, Steal and Traps skills. Rob from the rich, and give to you.”— In-game description
Fallout 2 (patched), Fallout Tactics
“You gain +15 to stealing and lockpicking. Steal from the rich, and give to you.”— In-game description
Fallout 2 (unpatched)
When attempting to pick a lock or pickpocket somebody, the difficulty of the opponent’s skill test to detect the perk owner increases by +1.