Dexter studies those closest to Arthur in an attempt to understand the psychology behind the Trinity Killer's actions; Rita's Thanksgiving-dinner plans are complicated when her full house gets even fuller with the addition of some unexpected guests; Batista sees some closure on a troubling old case; and Debra's continued pursuit of the Trinity Killer may prove a threat to Dexter.
Dexter learns the Trinity Killer may be taking his act on the road when the homicidal maniac plans an out-of-town trip. To gather more insight into the mind of the murderer, Dexter decides to accompany him, but isn't really ready for some of the shocking revelations of which he becomes privy. Back in Miami, a technicality is keeping Debra off the Trinity case, but she utilizes others in the department to get her opinions registered
Dexter knows it’s only a matter of time before Miami Metro discovers the Trinity Killer’s latest handiwork. Therefore, he has to work doubly hard to stay one step ahead of their investigation. Dexter has begun to realize that the closer he gets to Trinity, the more he stands to learn from this very different beast. Trinity hides behind a well-kept mask, and getting behind that facade will require some extra prodding on Dexter’s part. Meanwhile, Debra becomes frustrated when she finds herself shut out from her own case. She considers bending the rules in the name of justice, risking her career in the process. LaGuerta and Batista come to regret a major decision, and realize that by playing by the rules they may have painted themselves into a corner. And when the friction between Rita and Dexter comes to a head, Dexter gleans relationship advice from a most unlikely source.
Dexter is inspired to investigate the Trinity Killer on his own, while Debra blames herself for an event that was out of her control, and Rita realizes how little she knows her husband after discovering one of his secrets.
