At the end of Fall 1152, Midnight is depicted as being exiled beyond the scent border amid a pack of hungry looking wolves. While his demise is only implied and never shown, is it possible he could return to the territories or story line in general?
You can do what you want with your stories of the Mouse Guard. To wit, and stealing from pop culture…
That Mission probably has more bite if the Patrol encounter Midnight first and are given the chance to offer him forgiveness. If they do give him forgiveness, he repays them by betraying them anyway - he really is a bitter old bastard. If they refuse him succour and forgiveness, he flees into the night and betrays them - or you know, maybe the Patrol executes him, which would be pretty cool too.
I’m just making crap up to illustrate that there ain’t no canon, so go crazy