After discovering the Langstrom drive in Mission 1.1, you’ll have to patrol the streets of Gotham and gather clues.
Naturally, gathering clues involves beating up criminals, so first things first, let’s find some! Hold down on the D-Pad to use your AR Scanner, and look for white triangles that indicate crimes that are occurring. Find the nearest one, and grapple your way over to it. There’s no fall damage in Gotham Knights, so don’t be afraid to simply jump off the building you’re on.
After you take out all the enemies at your first crime, you’ll probably still need a few more clues. Use your AR scanner once again, find another nearby crime, and go beat up some more criminals. Once you’ve collected enough clues, Alfred will call you and let you know what he’s discovered about the drive. You’ll now need to make your way to the GCPD morgue — this will be indicated by a yellow objective marker on your HUD shaped like a building. The Batcycle is probably the quickest way to reach the morgue, since your character doesn’t have their Heroic Traversal skill yet.
Head directly for the spot indicated by the objective marker — it’s a rooftop across from GCPD headquarters — and once you’re there, a cutscene will play. Once it finishes, head to the top of the building northeast of you, by way of the rooftops in between (1). Once on the roof, head north across it, then drop down all the way to the alley behind the building — the diamond there indicates where you can enter the GCPD building (2).
Since ideally you’ll remain undetected for the bonus rewards, there’ll be a bit of stealth required in the next section. After going down the ramp and turning left, you’ll see some police cars with enemies nearby. Start sneaking and head quickly across to the right side of the area (or you’ll be spotted). Then continue around the right side of the near car, and sneak up behind the first policeman on the left and press Y to do a stealth takedown on them. Continue east, the way the policeman was facing, and turn right to head up the stairs — continue through the door marked Enter on your HUD.
Inside the building, continue forward up the stairs and into the exercise room. In the far corner of the room with the weights, there’s a hole in the wall you can grapple to, allowing you to enter a ventilation shaft.
Continue through the ventilation shaft, where you can stop and listen to some conversations if you like. You’ll eventually drop out of the shaft into an interrogation observation room — here, once again you can listen to some conversations, or just continue through and out of the rooms. You’ll enter a hallway — turn right and open the door on your right at the end of the hall.
In the next room, start sneaking, and hug the left side of the room (1). Once you pass the cells, the guard at the desk will be able to see you if you go slowly, so sneak straight past the desk and then grapple up to the balcony above him (2) and enter the evidence room.
Take two right turns and you’ll find a chest — then continue towards the red light that indicates the exit sign, and go through the door there. Turn right and go past the stairs leading down, then go left and open the chest at the end of the hallway. From there, you can jump off the balcony to avoid the first security camera (1), and then sneak towards the diamond until you can grapple to the second floor (2). The door here is locked, so you’ll need to sneak over to the sergeant’s desk and grab the keycard. First, you should disable the security cameras — instead of leaving the way you came in, head down the stairs and interact with the control panel on the left side of the doorway (3).
Now sneak down the hall towards the sergeant’s desk. Make sure the nearby officer has their back turned, then hold A to vault over the low barrier next to the desk.
Grab the key and go back the way you came, once again grappling up to the second floor. This time, you’ll be able to go through the double doors, and continue forward to the morgue. Head through yet another set of double doors, and you’ll be treated to a cutscene conforntation with Talia al Ghul. Once it ends, you’ll need to find Langstrom’s body. Continue into the next room, and you’ll see Langstrom on the first examination table. Walk over to his body and hold A to investigate.
Hover and mark the Blood Sample and the Blood Glucometer, then press Y to solve the puzzle.
With the Bioencryption Key discovered, you’ll need to escape the morgue, ideally without being spotted. Head past Langstrom’s body, following the exit signs above the doors. After Robin unlocks the double doors, you’ll be able to interact with them, starting a custcene. When it ends, you’ll need to get past GCPD to get out of the morgue. You can simply run past them if you want, but that’s not how Bruce taught you! Instead, sneak to the top of the nearby stairs, then grapple across the room to the balcony.
Drop down and exit through the doorway below — diamonds will guide you the rest of the way out. Once you get to the final set of exit doors, you’ll be transported into the garage, already on your Batcycle. Follow the yellow GPS arrows and return to the Belfry, ending the mission. You’ll have to walk up to the green Belfry icon and interact with it — simply parking where the GPS tells you will not let you re-enter the Belfry.