Location: West Wing, fixed location
Rescue Reward: Machinegun
From the Manual: Your grandfather Frank Benjamin Patterson was a great forensic specialist at Scotland Yard. He is the eldest of the Patterson family and has spent a great deal of his off-duty time safari hunting.
Like the other West Wing hostages, Grandpa's location is randomly determined when you begin a new game, but he will always appear in the same room even if you reload from a previous save game. An avid hunter and macho cop, Grandpa's a bit too old to help you fight monsters, but he brought along a handy machine gun in his trunk and will give it to you as soon as you bring him back to the Sanctuary. The machine gun is a powerful weapon that allows you to kill multiple enemies and makes the final boss fight much easier, so you should try to invest as much effort into rescuing Grandpa as possible.