Quincy is a character in Strife.
The player meets Quincy in a Hospital, in the Bailey of the fortress. He tells the player how to reach the Bishop and about the Maulers in the Warehouse. Quincy also has a assistant who helps him selling medkits. But before the player has talked to Quincy, his assistant won't sell anything.
The "five-finger discount" Quincy mentions is a slang term for shoplifting.