Follow the waypoint to the building and scan the two bodies, the lone sword and the blood splatter. Then follow the blood trail, unlike the old batman games you do not need to look at ever spot, If you find one further along the trail it will register that one and allow you to continue. The trail will lead you over many rooftops and into a fight at 3019, 2362. Beat the thugs and continue following the trail which will lead you to a duct on the roof of the hospital at 2938, 2112. Power down the generator and go down the duct. Fight the group of enemies and activate detective mode to find the blood spot near the door. Above where you fought the enemies you can grapple to a grate that will lead you to a switch to restore power. After you hit it navigate your car around the building to find a ramp that will allow you to jump up to the winch. Hit the switch again and travel through the door. Use the electric charge tool to get under the elevator. After you climb up you will see a sparking fan on the wall ahead. Throw a remote batterang through the hole just above it. Navigate the batterang to the sparking wires in the hall and then back into the room where the fuse box. After you go through the door use the evidence scanner to reconstruct the last moments of the assassins life. Scan all the switches and then hit them in order of decreasing height. After a cut scene you will get the achievement.