Where would the Meursault canto even fit in the story? I see three points of where you can kick start the City plot
A. As soon as the Sinners arrive he reaches his breaking point and kills a man in hot blood, causing all sorts of problems thereafter
2. He’s on the run already and returning means the local authorities bring him in for his informal trial, putting the Sinners through the Districts version of a judicial trial
3. He’s actually broken out of prison before his death date came so returning means the Wing is on everyone’s asses now that they know their man came back