It’s hard to believe that Castle’s fifth season is almost over. In “The Human Factor”, Andrew Marlowe and Co. plant the seeds of what promises to be an emotional season finale and an important change in Castle and Beckett’s relationship.

When Dale Tanner’s car blows to pieces along with its owner, the team finds it extremely hard to investigate – on accounts of having all the evidence wiped away by the feds. The car is taken away, Tanner’s phone records are deleted and the website where he posted potentially damaging information about all sort of grand organizations is taken down. Under these circumstances, Beckett and Co. are forced to start from scratch, with nothing more than the manner of death. When it turns out that not only was there never a bomb inside of the car, but that it exploded when a missile was released from a military drone and into it, the case takes a surprising turn.

The military doesn’t collaborate, and neither does Jared Stack, the District Attorney investigator who manages to tail Beckett and Castle throughout half of the investigation. When Beckett makes a deal with the DA, however, Stack shares his information with them. The main suspect is Simon Warburg, an expert on drone technology who vanished into thin air one year prior. When they track him down, after visiting a bookstore that made my bibliophile heart sing a hallelujah, he proves himself innocent and very much concerned about how easy it would be for programmed drones to kill innocent people. He insists on the need of people, of the human factor.

He also tells Castle and Beckett that he sent his software to Tanner so he would publish it on his website and thus prompt the Pentagon to withdraw the project – but that when Tanner said it would be highly dangerous to have that software seen by all, he agreed to keep it a secret. However, when he got the file back, he realized somebody had copied it. After fruitlessly interrogating Tanner’s partner, Omar Dixon, and briefly suspecting both Tanner’s wife and the woman he was cheating on her with, the team finds the real killer: Sean, Tanner’s son, whose years of pent up resentment against him exploded upon finding out about his father’s affair.

Beckett’s efforts while working this case might have had long-reaching consequences: Stack, impressed by her efficiency, suggests that she interviews for a position working for the DA in DC, with complete autonomy and cases of the highest significance. Will she take it? We’ll find out – along with Castle – when the season finale airs next Monday on ABC. Make sure to tune in!