You need a password to enter the house of Voodoo Gentleman. Interact with the small window on the door.
This is the low-spoiler guide for "Password to Voodoo Gentleman." puzzle in Gibbous - A Cthulhu Adventure. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.