As part of the Afternoon Delight Visionary Lead, you'll need to solve the Deathloop data cassette puzzle. Doing so will open Charlie and Fia's secret hideout, providing you with yet another way to kill both Deathloop Visionaries. The solution is randomised, but the way you solve it remains the same each time. With that in mind, let's get started.
Deathloop data cassette puzzle: How to solve it
To solve this puzzle, you'll need to find four pieces of Fractured Art in Fia's underground bunker at Fristad Rock. Head over there at noon to find them all. You're looking for large green spraypainted Pictograms, that are often a series of squiggles, circles, and other shapes. The ones you're after will be green on a red background, so look through her base until you find them all. Remember, their location and types will be randomised each time, so keep searching until the quest updates.
They can be found on the walls, floors, and ceilings. They're big enough to be hard to miss. After you've found all four, go to the edge of the tundra that meets the coastline and head toward the ruined plane. You'll soon reach some stairs, so climb those and you should see a door with the numbers 0 and 9 beside it. You'll then come across Charlie's Obnoxious Machine.
There should be a set of blueprints on the machine. What you need to do is study it and see what Fractured Art you've found matches what number of data cassettes. Press these cassettes in the right order and the door will open. You'll also be able to find the combination to the safe in Yerhva on the machine, killing two birds with one stone.