This is an optional objective given to you by Callista as you leave the Hounds Pub for Samuel before commencing mission two - High Overseer Campbell. You will be tasked with keeping her uncle, Captain Geoff Curnow, alive.
There are multiple ways of making sure Curnow survives. If you choose to poison Campbell, you will be presented with the option of leaving Geoff’s glass alone, and doing so will ensure his survival. You can take him out non-lethally, and hide the body. You can follow both of them downstairs to the Overseer’s secret room and kill Campbell before he kills Geoff, or you can simply kill High Overseer Campbell as soon as you spot them in the meeting room. Note that killing Campbell in the meeting room will cause Geoff to attack you. Simply block his attacks and escape through the meeting room windows, and Blink your way free.
The final method is to have a body in plain sight once they enter the room. Geoff will panic and flee from the the area which will result in the trophy unlocking, while Campbell runs to the safety of his secret room in the basement.