O'Conner uses a few instances of irony within the narrative and these are as follows:-
1) Although the Grandmother likes to think of herself as respectable and honest she is quite a malicious character whereas the misfit of society is respectful and polite
2) Misfit looks beyond superficiality i.e. he is honest about himself and doesn't try to be anything else whereas Characters like Red Sammy judge people by the car they drive
3) Bailey's children come from a middle-class family and are well cared for yet they're rude and spoilt whereas the little 'negro' child in the road who does'nt even have proper clothes to wear is friendly and waves to them
4) Even though the misfit is obviously going to kill the Grandma as well she has a moment of 'Grace' and reaches out to him offering acceptence and recognition as a fellow human being - something the misfit hasn't come across before.
Hope this helps