i was thinking the same thing. i have a feeling that Arthur's family may cover for Dexter/Kyle
I had this feeling that Jonah would have said something along the lines of
'He helped us.' Causing Quinn to doubt his suspicion and start thinking about what Dexter really does. Which causes Quinn to meet Lumen.
I liked how Dexter didn't tell Lumen everything and blamed Rita's death on his reason for killing people.
