Leaving the basement is not a difficult task, as there is only one main path leading to the exit. On the way, however, you may choose to explore the area you walk through, including individual cellars. It is worth adding that some cellars are inhabited, which can result in having several conversations. What is more, the cellar number 028 is tied to the case #776, whose walkthrough can be found on a separate page of this guide.
Begin a linear walk through the basement. You can tell you are going the right way by the increasing numbers of the cellars you pass by. Ultimately, you must reach the door with the EXIT sign, as shown in the picture.
There is a code panel by the basement exit door. Interact with it and do not worry that you do not have any spare four-digit codes, as you can just find this one out by hacking the panel. However, this way you will only learn the first three numbers. The last one you must guess by trial and error. In our case the correct combination was 4004.
After leaving the basement you will experience hallucinations. Follow the corridors until you get to the door with an intercom, and you will have an unusual conversation.