On the"Dead Man Walking" level, after achieving the "Locate the Nanosuit Deep Scan Cradle: Locate Gould" objective, there will be an elevator at the end of the level. Take the elevator down as instructed. When the elevator door opens, follow the hallway. After the first right turn notice the security camera next to some servers. Jump over the red rope and get close to the switch on the right. Hold [Action] and a red light will appear. Return to the elevator that you used, and jump over the red rope to reach a second elevator. The switch will now be lit. Hold [Action] again, as instructed. The elevator doors will open, showing a C.E.L.L. dance party.