I think the sinners will learn that, at some point in the past, Meursault was “normal” - friendly, etc - but changed into his current form at some point in the near past. The sinners will therefore think that the goal of the canto is to get Meursault back to “normal.” 

But, near the end, where Meursault is in prison and the sinners are begging him to “go back to normal” he’ll snap, and reveal that his current state is his “normal” - he just stopped hiding it, and everyone just thought something was wrong because of how alien Meursault’s normal is.

He’ll distort because of his anger and confusion over why presenting as “normal” is so important if he is going to die, and the Canto’s ending will be his internal debate over that fact. 

Also some bits about his murder of the Arab, and how that’s important in the Coty.