For this mission, you need to collect two samples from the Spiky Wall Climber plant. When you begin, turn around and collect the Secret Sly Mask near the entrance. Stealth kill the two guards in the middle of the room, then climb the rope near the big doorway opposite the entrance. Swing from the hooks, making sure not to stay on them too long, or else they sink down a bit. Launch yourself after the hooks and then swing onto the final platform with the plant. Smack it to make it open, then press Circle to grab the seed.
Drop down and go through the doorway from before. If you climb up, then you'll see the electrified bugs from an earlier mission blocking the way to the poison plant. If you look down on the floor, you'll see the lamp surrounded by wooden spikes. Go to the lamp and wait until the spikes go down, then hit it, sprint to the rope, climb it and then launch yourself to the poison plant. Smack it open and grab the seed to finish the mission.
