Can I complete optional Tasks later?
In Dishonored, can you complete optional tasks after completing a mission?
I've just killed the first assassination target and am about to climb in the boat, however there is an optional task for the old granny that I've not done yet.
Sure, so long as mission completion doesn't in some way cut off your access to an NPC or area required to complete that optional objective.
Until you get back on the boat, everything you do still 'counts', regardless of whether you've achieved your primary objective already.