Quick recap
Dexter is now Harrison's dad and barely sleeps between family, work and kills. Frank Lundy returns, now retired, chasing the Trinity Killer, who has followed the same pattern for about 30 years. Lundy is killed and Debra is shot. Dexter finds out Trinity is Arthur Mitchell, a churchgoing family man who runs a home-building charity, and gets close to him under the fake name Kyle Butler to learn how he balances two lives. The shooter was Christine Hill, Arthur's daughter, who confesses to Debra and kills herself. Arthur learns who Dexter really is. Dexter kills him in the end, but when he gets home he finds Rita dead in the bathtub and Harrison sitting in her blood.
No spoilersOpens once you mark the title as seen.