Charlie is one of the bosses you will need to hunt down in Deathloop. He can be tracked down in Updaam at noon, where he will be hanging out in a strange castle made up for childish games. He will have the Shift Slab, and if you want to get your hands on it, you will need to kill him. As he has the ability to shift around, this can be easier said than done.
Make sure the time of day is noon and then head to Updaam. Keep to the left when deciding which tunnel exit to use, and make your way up the street to the main road. Hack the sensors on the left and head through there and cross the bridge.
Once that is done, cross the bridge and it’s time to head inside the strange Fun HGuse building ahead. Keep to the right, skirting along the outskirts of the ruins and avoiding as many enemies as possible. Make your way to the rear of the open courtyard area and head through the double doors there.
Go straight ahead, taking ou the guards, and you will come to a pit filled with green gas. Turn right and follow the walls to get to a staircase that will bring you upward. Just keep going up level by level until you reach the very top. You will need to be careful along the way, as lots of guards can be found here. When you reach the top floor with the backend of the rocket and the orange cursor hanging above it, go through the double doors at the back of the room on the left.
Take out all the trip mines, then head outside and take out the rest. Hack both the turrets in the office room and head inside. In the first room, grab the tape recorder with Fia on it, then head down the corridor. Go into the back room and interact with the terminal with the yellow screen that you can find on the table. Read the messages, then go back to the previous room and grab the picture just on the left side of the door. You will now know that Fia and Charlie are something of an item, and it should be possible to take them both out at the same time.
For now, make sure your tracker is set to the Shift Slab in the Arsenal Clues menu, and you will be able to see where Charlie keeps teleporting to below you. Go back to the room, wait near one of the spots he appears, then jump out and snap his neck when he shows up and grab the Slab. Make sure you absorb the Residuum from his body and infuse the Slab so you can keep it after the day resets.