Reach the chapel in the Old Quarter | The City Thief Guide
Last update: 11 May 2016
After you return to the clock tower [Stonemarket - Clock Tower Plaza] go to the upper floor, which will start a cutscene of the meeting with the Queen of Beggars. You can now leave the tower and go South-Westwards. In order to get to the Old Quarter, you need to reach the big gate, marked by the game, and squeeze between the crates [Stonemarket - Grandmauden].
After you enter the Old Quarter, go West and slow down after you approach the watchtower. This tower is being occupied by a guard with crossbow an, apart from that, around the tower there are two other enemies. You should especially turn your attention to the opponent that is patrolling the area around the tower and approach the tower, only after he goes left (to the South).
You need to hide quickly because the guard does not stop anywhere. So, if you are not quick enough, you may bump into him and it is going to be difficult, then, to find any hiding place. I recommend that you hide in the wardrobe, located at the back of the watchtower, and wait for the opponent to walk past Garrett. Leave the wardrobe and, in the spot shown in the first screenshot, use the claw to get to the balcony above.
Use the planks above to get away from the tower (this way, you will avoid the confrontation with the guard at the tower). Go Southwards and turn South-west. Your destination is the gate to the cathedral. Interacting with it results in the beginning of the seventh chapter of the campaign mode.
Note - Garrett will not return to the City, after you have completed chapter seven, and start the last, the eighth, chapter automatically. Therefore, I recommend that you complete all of the available side missions, before you start the seventh chapter, and take with you as much supplies as you can.