There is 1 Dead Ghost to be found in the Overwatch. They can be collected on any mission or during a patrol. Each Ghost can only be collected once per account.
Ghost 1[edit]
Head into the Overwatch. From there just head through the room and through the door at the far end with "Clovis Brav Exoscience" on it.
Once through the door, going up the stairs and to the left. Look for the set of desks on your left. Head for the desks on the left.
Underneath the left-hand side of the desk you will find the Dead Ghost:
