After analyzing the clay sample, the Knights have tracked him to the Dixon Docks. In this mission, we’re off to investigate what the malleable man is up to. Note that in order to access this mission, you’ll have to go into your Case Files and select the Clayface file, then select this mission from the list and launch it.
You’ll begin the mission perched near a warehouse. Jump down and head inside (1), where you’ll need to scan some Clay Residue on the ground (2) using your AR scanner (, ).
This will allow you to follow a trail of foot clayprints that lead outside, and then up onto the rooftop of another building (1). Continue following the trail, and it will lead you across the roof. Then, you’ll have to jump or grapple across the gap to continue following the trail as it goes inside another building (2).
Inside, follow the trail to a vantage point where you can see three gangsters and one of the Clayface muggers. You can attack the gangsters, but you may also be able to get them to run away by making noise (walking/running instead of sneaking) behind the cover near them. This will allow you to sneak up on the Clayface creature without having to get by the other enemies.
However you handle it, a cutscene will play once you’ve defeated the Faceless Mugger. When it ends, the chase is on! Well, not really — you don’t actually have to keep up with Clayface as he runs away, as he will politely wait for you if you fall behind. Follow the Bugs Bunny-esque crumbling pavement (1) — it’s hard to spot, but Clayface will pop out every so often and make it obvious where he is. He also leaves clay marks from time to time (2), which helps with tracking him. The chase will end with an epic Batcycle jump, and then you’ll need to drop down into the sewers to continue the pursuit (3).
Continue following the clay trail — you’ll have to crouch to get into the ventilation shaft (1). Make your way through it, turn right when it ends, and head to the large fan at the other end of the hallway. Crouch to get through the metal screen there, and you’ll see a group of Clayface muggers below you to the right. You can utilize stealth to take down at least a few of them, and there are also a number of explosive barrels that you can destroy by holding /to aim and then pressing /to shoot at the barrels (2). After defeating the 5 Clay Mimics, you’ll be able to squeeze through the narrow gap indicated by the door icon (3).
One loading screen later, you’ll be in a sewer tunnel. Go left as the objective marker indicates, and turn right at the junction (don’t worry about the chest, we’ll grab that in a sec). Head up the clay-covered stairs, again following the objective marker. At the top of the stairs, you can check out Clayface’s movie script on the table with the typewriter, then continue down the stairs on the other side of the platform (1). Wait for the flames to subside, then go past the broken pipe, turn right, and continue through the doorway (2). Turn left, and you’ll find the aforementioned chest.
Go back the way you came, and continue straight after going through the doorway. Follow the objective marker into the tunnel, and slide down into another cutscene. After enjoying a bit of revisionist history, you’ll begin a boss fight with Clayface and his Homonculi.