Chapter 4 Walkthrough: The Data Heist, Step by Step
Two routes through the server tower, how to avoid the alarm cascade, and the dialogue choice that unlocks the hidden ending.
Chapter 4 is the first mission where Neon District 2 lets you fail quietly. Trip the alarm cascade and the chapter still completes, but you lose the Ghost rating and the hidden ending closes for good. Here is the clean route.
Entering the tower
Take the loading dock, not the lobby. The dock guard patrols on a 40-second loop; wait for him to turn toward the trucks and slip behind the crates to the freight lift.
Floors 12 to 18: the server stacks
Two routes open here. The vent route is slower but never triggers a camera. The catwalk route is faster and gives you the Overseer's keycard, which you need for the hidden ending. Take the catwalk and disable cameras in the order 3, 1, 2; any other order starts the cascade.
The dialogue choice
When Rho asks whether to wipe the backups, pick "Copy them first." It looks like the greedy option but it is the only one that keeps the evidence Chapter 9 needs.