Falling from Grace is a main mission under Clan Kelley in Watch Dogs Legion.
Your task is to go to Sandstone Residence and stop Mary Kelley for good.
Here’s a walkthrough of Falling From Grace in Watch Dogs Legion.
Confront Mary Kelley
Head to Sandstone Residence in Islington and Hackney.
To enter the building, hijack a news drone and enter through the top window.
Continue to make it through the vents.
You’ll then reach the ground floor area. There are guards in the area. You can get rid of them via the traps.
Locate the hidden security room
You’ll be required to find the hidden security room.
Summon a spiderbot first. The device is in the area.
Use the spiderbot and unlock the outer door that leads into Sandstone Residence, by interacting with the panel beside it.
Then, get back to your operative and enter the residence through that particular door.
Get to the common area / lobby. There’ll be a lot of guards inside. You should take some of them out using the traps first.
Next, head upstairs. Look for the big clock and there’s a movable light-bulb handle. Turn the handle and the secret room is unlocked.
Disable the microchip control mechanism
Interact with the keyboard to disable the mechanism.
Power up the lift
Go back down to the lobby / common area. There’s a switch to interact with to power up the lift.
While waiting for the lift to power up, you need to survive.
The best way to survive is to find a corner to hide from their view. If you’re hidden, the enemies don’t seem to keep coming.
Defeat Mary Kelley
After the lift has been powered up, go towards the lift marked on the screen and use it.
Head to the door at the end to trigger the cutscene.
The mission ends after the cutscene.