"Take care of Officer Jack" for Mira is a quest intended for stupid characters in Fallout 2.
Mira has recently went through a very severe divorce with Jack, an NCR police officer. Player character with less than 4 Intelligence and Strength of at least 7 will be asked to take care of her former husband: Kill him.
The quest will depend on when the player enters the downtown area. At nighttime (Mira will provide a rope slung over the wall, allowing the player to enter bypassing the forcefield), Jack will be found inside the police station. If the player waits until dawn or enters during daytime, Jack will be found at the power plant, threatening to blow himself up.
Killing Jack at that point is the easiest method, as once he begins his routine ("Bite me!"), he can be shot down freely, earning 2000 XP and a HK P90c from Mira.
Non-stupid characters can obtain this quest as well, by exploiting Psycho or Mentats withdrawal to lower their intelligence. Note that to obtain the reward, they have to remain stupid when talking to Mira.