Get Gizmo's confession

 is a side quest in the original Fallout.

Walkthrough
After the Vault Dweller speaks to Killian Darkwater for the first time, a man named Kenji equipped with a Colt Rangemaster hunting rifle enters the store saying "Gizmo sends his regards" and fires at Killian. Once the lone assassin has been dealt with, Mayor Darkwater asks the player to obtain a confession from Gizmo so he can lock him up or take him down. There are a number of ways to do this. Go to Gizmo's office at the back of his casino. Here, you can either plant the bug on Gizmo with the steal skill or persuade Gizmo to hire you to assassinate Killian while you have the tape recorder in your inventory.

Rewards

 * 500 experience points
 * The Vault Dweller can take something from Darkwaters General Store. This can be either 5 stimpaks, a doctor's bag, leather armor or a shotgun with some shotgun shells.
 * Killian offers Take Revenge on Gizmo quest.