How to get the card key?

[card key?]

Hi, how can I get the card key in Chronopolis?

On the 4th floor to the left there is a wall blocking the robot...??

[Shotgunnova]

Lesse...

1) Get to 2nd floor and release LV2 Lock
2) Go to 4th floor via elevator and find ghosts talking about chief
3) Talk with chief at the ground-floor dock
4) Return to 4th floor and find Card Key in chest behind a Combot