Use the elevator and go to the concourse. Wait until soldiers go away. Approach the Cartridge and return to the elevator. What a surprise - Cletus has freed himself and got a gun! After the conversation Argus shows up. Use all dialog options - Rufus will agree to give back the implant.
In the next scene Cletus tries to convince Goal that Deponia is uninhabited so it can be destroyed. After few moments they go back to Elysium. And Rufus's future is not so bright - Organons' soldiers wants to kill him. Plus he failed to throw out the cartridge!
Turn to the Ramp and then grab the Handle of the flying device. Rufus and Prime Controller will fall down from the tower.
In the last cut-scene Bozo asks Rufus, if Deponia is safe. But this is not anymore in his hands ...