HOW TO START THE MISSION
There are two things that have to be in place in order to start and complete the side mission.
First, you have to Visit Otar during mission 4 and agree to do him a favor in the future. Otar conversation:
Straight talk, Compliment, Straight talk
Second, during mission 7 you have to either kill or warn GalloisTHE RED QUEEN
Now that you have completed these two steps, you will get a message from Masa Kadlek when you return to prague for your second visit.
Visit Masa in the red light district and talk to her about her relative Dominic and the agree to grab him from the Dvalis. BREAKING IN SILENTLY
Your best option is to go over the roofs. Exit The Red Queen, go to a courtyard and enter through a balcony by jumping on a roof and then climbing a ladder. FINDING THE SECRET ROOM
Take the stairs in the apartment complex and break into the middle room (code 0666). There is a secret button at the TV stand. Press it, turn around and hack the laptop to shut down all security cameras. GRABBING DOMINIK
Now that you don't have to worry about cameras, you can go downstairs and take everyone out silently, including Dominik. You recognize him by his tattoos.
Drag him out the same way you came in. You now have to throw him off the balcony into the trash underneath it. Make a save before you do this since it can happen that he lands next to the trash, which means he dies and the mission fails.
Now you only have to put him into the garage and close the door.