Gilbert | Side quests Bloodborne Guide

You can talk to Gilbert after you leave Iosefka Clinic, at the beginning of the game.

Gilbert is one of the first, if not the first dweller of Yharnam, who you can talk to across the window. You find him in front of the first lit lantern. By talking to him several times, throughout the entire game, you will learn several hints and curiosities about the game world. After you defeat Father Gascoigne (before the fight with Cleric Beast) or after you defeat both of them, Gilbert will also act on your side - you receive Flamesprayer from him.

After you return here, you find Gilbert turned into a beast.

Gilbert cannot be saved. You will see it, after you have defeated Rom, the Vacuous Spider. Gilbert breaks out the bars in his window and will be around as a beast, which attacks you. For defeating the opponent, you will be rewarded with Clawmark rune.