Make your way out of the vent and you'll find yourself above a mercenary having a conversation through an intercom. Take the ladder down and find some shadows. Wait till the merc ends the conversation, then stealth kill him.
Continue through the door into the control air for the cell blocks. If you turn left immediately, you'll find a place to drop down into the interior part of the room. You'll also be hidden here.
You're facing three mercs in this room. There's some decent places to hide, especially now that you're under the floor. Bide your time and strike to kill one or all of them without the others noticing.
Bounty! After the room is clear, stand facing the two small staircases that lead up to the area where you entered. Duck down and go under the one on the left to find a hole. Crawl through for Bounty Card 59.
With that done, collect a code card from one of the bodies. Take it to the terminal and you'll be able to open the door to Cell Block 12B on the far left of the room.
In the cell block, walk down to the terminal and open up the cells. You can then start talking with the prisoners.
You need speak with Dacher, then Silverman, then Jaylor. You can speak with Bonner also, but he doesn't have much information. You'll now receive a series of other missions to complete in order to get where you're going.
Margo's Tooth
Jaylor tells you to assassinate someone named Margo in the berthing area. Backtrack out to the main terminal and press it to open the door to berthing.
Enter and head to the right. There's a nanomed machine here if you need it.
Bounty! Head down to the left to the dead-end hallway. You'll find Bounty Card 53 here.
Now proceed to the green door down the ramp to the right from where you started.
There are three mostly unarmed men in the hall. You should be able to clean them up easily.
Bounty! Bounty Card 28 is on a small table amidst some other garbage on the right side of the hallway, about haflway down.
Keep moving down the hall. You'll enter another area of quarters and have two more guys to fight. Kill them and continue on.
Margo's on the run now. Keep following him around the corner to a hallway with space on one side and doors on the other. At the end of the hall is a bruiser named Iron Lord. You'll have trouble countering him, so let him attack and then slice him up when he's open.
Achievement Alert! Killing Iron Lord nets you the Melee Master Acheivement.
Bounty! Check the rooms for some various goodies. Bounty Card 24 can be found inside the second room you pass.
Past Iron Lord is a staircase. Ignore it, as you can't go anywhere from up there yet. Past it and around the corner is a grated vent you can access. It's on the floor to the left.
At the end of the vent, drop down and fight Margo. If you're quick, you can counter him for an easy win.
Bounty! After dispatching Margo, check the nearby table for Bounty Card 47.
Grab Margo's Code from the bed against the wall. Exit the room and prepare to deal with two more mercs.
Another merc is waiting for you at the entrace to the berthing area. Kill him, heal if you need to, and backtrack to Jaylor. That completes the Margo's Tooth mission.
Backtrack out of the cell block and turn right to find the locker. Open it and grab the screwdriver.
Vent Tool
More prisoners are awake now, so go and talk to them for some more information.
Head out of the cell area and back through the door where you entered. Just outside the door is a hatch you can open with your screwdriver. Drop inside and crawl along until you come to an opening. Just below is a drone on patrol.
Drop down and stay hidden. Wait for an opportunity and kill the drone, then use its gun to blow out the window on the right side of the hallway. Proceed out onto the catwalk there.
Mercs patrol the wall to the left and a spotlight is running along the wall to the right. Wait for the light to descend to the bottom, then run over and quickly climb the ladder to the top.
You'll need to continue to ascend by climbing the square ledges scattered around. Try to move fast and wait for the light to pass you by ducking into the interior parts of the structure. Otherwise, you'll take fire from the merc on the far wall.
TIP: Remember to press Y to climb ledges you can reach from a standing position. You'll also need to hit Y to catch ledges you jump to.
Bounty! At the top of the structure, turn left to find Bounty Card 54. If you wind up on the ladder to the right, you've missed it.
You'll eventually make your way up to a vent you can enter. Take care to avoid a drone on patrol as you exit at the far end.
Now look for a hole in the floor just behind a crate in the center of the room. Drop down and sneak up on the mechanic working on the floor. Kill him and grab the tranquilizer gun on the other side of the sparking hole.
Back out and deal with the drone that just appeared. You can zap it with the stun gun, then kill it with another weapon while it's dazed. Proceed through the door it came through.
You'll need to ascend to the upper level of this room and dispatch around four drones to do so. It's fairly shady and you should be able to deal with the lower level drones without attracting attention from the upper level ones.
You can reach the second level by climbing the ladder on the far side of the room, or scaling the blocks as you enter the door. If you take the blocks, quickly kill the drone on the catwalk in front of you. The tanquilizer gun makes this pretty easy.
Get up to the second level when you've killed the drones and jump across the orange, stalled elevator to the door on the other side. Go through.
Bounty! You'll see Bounty Card 6 immediately to your left, inside a crawlspace.
Sneak through this crawlspace and then ascend the stairs. Stay against the left wall and hidden and take out the two patrolling drones as they come down.
Continue up and take the big door. Immediately go left and get behind the crates there. A merc is searching for you with a spotlight. You need to move behind the crates to the right side of the room, then turn around and head toward the back of the room to find an elevator. Just step onto it to make it work.
Bounty! Check the top of the crates at the front of the room. Climb up when the light sweeps away and grab Bounty Card 39, then drop clear.
At the top of the elevator, hide behind crates again and cross the catwalk to the left. You'll need to climb some crates at the end to reach the other side. Another elevator waits.
This time, when the spotlight leaves your side of the room, follow it, staying just clear. That'll help you avoid the large gap in cover positions. Take another elevator up.
On the fourth floor, you'll be attacked by two mercs as you go move along the catwalk. Kill them quickly to avoid being shot at by the others. Then continue hiding from the light. Make your way into a hallway at the end of the catwalk. It houses a nanomed machine.
Now duck through the door just to the right of the entrance to the hall. Proceed to the end and you'll see a drone below. Drop down on it to kill it and grab the Tool Parts off the ground nearby. Press the elevator button to descend.
You'll have to use the drone's gun to fend off the mercs in the shaft. Look for them on the left side of the room. Before long, you'll see two more mercs -- one in the distance straight in front and another to the right. Kill them fast or they'll mince you up.
TIP: This drone gun doesn't run out of ammo, so be liberal. You won't have an easy time seeing your targets and you can't hide form them, drop the drone or jump off the elevator. So just find a spot to shoot at and unload until you're safe.
At the bottom, you'll be back where you started. Climb the ladder and follow the pipes to a catwalk. Take it under the glass room to the other side, where you blew out the lower panel. Climb back in and look for the vent to your left.
Drones now are patrolling the cell block. Sneak through the crawlspace and try to kill them with stealth. One is a regular drone, the other a white merc-controlled model. It's slightly harder to kill.
Take the tools to Silverman and she'll build a vent tool.
Achievement Alert! You'll get the Opening the Vents Achievement.
With the vent tool in-hand, go talk to Dacher. He'll request a Data Pad and give you two new missions.
Head back to the berthing area. This time, you're expected, so watch out for merc-controlled drones. The first is down the hall to the right, standing guard at the doorway when you enter the berthing area.
TIP: Check the big table on the left side of the first barracks area to find a tranquilizer gun, if you don't already have one.
Continue down the hall to the door past the first set of bunks. You'll come across another drone. Zap it quickly and finish it.
Two more flashlight drones are waiting in the next hallway. Hug the wall on the left and get close with your tranq gun. Tag the drone on the left. The one on the right should totally ignore the commotion. Zap it too and kill both.
Keep moving. You'll enter the hallway where you found Margo and Iron Lord. There are four drones here, but only one is actually on patrol. Give it the slip by ducking into the nearest bathroom on your left.
When the drone turns, get close and assassinate it. Then move up and kill the drone facing the corner just ahead.
You'll see two more drones standing still near the lockers at the back of this area. You can deal with them if you really want to, but it's much easier and safer to ignore them entirely. Just head up the stairs, follow the catwalk all the way around to the right, and open the vent shaft to end the mission.
Drop out of the vent and take the nearby green door. There's a nanomed machine if you need it.
The next room is the berthing area mess hall. It's huge, stretching like a hallway in a large circle. It has no fewer than six merc-controlled drones in the first half, so be careful. Keep clear of their flashlights and use your tranquilizer gun to turn them into regular drones.
Bounty! As you enter this room, look for a television screen with a grate nearby. Blast the grate with the tranq gun and you'll find Bounty Card 46 inside.
Stick to the sides of the room and keep clear of the drones. If one sees you, the rest will come running. You'll deal with the first right away, on the right side of the room. Three more are further in. Move slowly and take your time.
After you've deal with those four, two more will be patrolling at the first corner. Use the equipment in the area to your advantage and you shouldn't have a problem. Then proceed through the mess.
Bounty! You'll soon come to a staircase that leads up to some more tables. Go up there and look for Bounty Card 29 on the middle table.
As you proceed on this raised area, look for a pipe running along the wall on the right side. You should also see a flashing vent ahead, above a door. Stand on a table and press Y to grab the pipe. Shimmy along until you can climb up to the vent.
Proceed through the vent until you come to the exit, back on Cell Block 12B. Kick out the grating and sit tight a second. A merc-controlled drone will appear, just in time for you to drop out of the vent and assassinate it.
Bounty! Climb up on the crates near the vent to find Bounty Card 58.
Head down the hall and to the right toward the Comm Station. Two more drones are patrolling ahead. Backtrack to find smoe place to hide from them and kill them when they're apart.
When you're clear, advance into the larger room and take the door to the right.
Bounty! Bounty Card 30 is waiting on the other side of all those crates.
Return to the last room and take the other door. Quickly sneak up behind the merc at the comm station and kill him. Grab the data pad from the chair beside him.
Achievement Alert! Turn around when facing the comm station and go to the wall on the right, beside the big floor vent. You'll see a sign that reads "Margo's Locker." You should be able to open it because you grabbed Margo's code from his room when you killed him. Opening the locker nets you Margo's Shotgun and the Margo's Locker Achievement.
Return to the vent and take the other hallway to Cell Block 12B. You'll emerge in the control room. Follow the hallway right and take the datapad to Dacher.