In Chapter 7 (Healthy Carrier) of Vampyr you get the objective Locate the secret passage.
This chapter is just one big castle, the problem is it doesn’t show you a marker for the secret passage.
Where to find Secret Passage Location:
Step 1: Start by looking at the big picture in the downstairs entry hall (where some rats are). Press / to use your vampire senses when looking at the picture. This reveals two red symbols: A moon and a sword.
Step 2: Go to the dining hall (also downstairs). There’s a long dining table, a fireplace and some pressure buttons on the walls. Hit the pressure buttons that show the moon and the sword as detailed on the screenshot below:
Button #1: Moon (in back of the room by the windows):
Button #2: Sword (on the right side of the fireplace):
Hit both of these buttons without hitting any other and the fireplace will open, thus revealing the secret passage. Now enjoy the rest of the chapter, the Vampyr story is almost complete.
That’s all there is to it — just hit the two buttons to locate the secret passageway.