'Criminal Minds' season 12 episode 9 spoilers: Rossi gets his annual birthday song from a serial killer

In the spirit of the season-long arc of revisiting the cases of previously captured serial killers, "Criminal Minds" mines an old but particularly notorious one in Thomas Yates (Adam Nelson).

The case of the aforementioned perv has been going on for too long now, tracing back to Rossi's (Joe Mantegna) early days with the Behavioral Analysis Unit (BAU). But the story only came to life back in season 7 with the episode "Profiling 101" in which the team attends a symposium at a university Criminology class and they chose Yates as the ideal subject matter to discuss. But just like every year and true to the deal he worked up with Rossi, Yates is back to reveal new names from his catalog of body count that has yet to be found over the course of the years. And cunning as ever, the psychotic criminal forces the BAU veteran to visit him in the penitentiary for an annual one on one.

What is interesting, however, is that, in retrospect, there is not much more that is left to his story in terms of committing brand-new crimes. The murderer has been locked up for quite some time and the only thing that keeps Rossi from agreeing to the arrangement is his personal goal to bring closure to the families of Yates's victims. So when Rossi receives a personal call from Yates, it more likely means that there is something new that the latter will unload on the former. It is also important to note that at the tail end of the call, Yates says "Come back Dave" which may mean that at some point in the recent past, Rossi has stopped visiting him. Or maybe they have just finished the long list already. Whatever the catch is, the team needs to step up their game to finally be able to put an end on the particular unsub.

In some sort of deja vu, the premise of the episode also has the BAU team talking in front of a crowd, this time for the unit's newest recruits. And given Yates's prolific history of killing, he is once again the ideal example for unsubs. Unless, obviously, that instead of a lecture, it is one of those briefings the BAU holds to decode Yates' end-game.

Yates actually plays a hand in the overall storyline of "Criminal Minds" as it was the first case that Hotch (Thomas Gibson) and Rossi collaborated on. At that time, one of the unit originals were hard at working on Yates' game when they tapped the help of a young Hotch who was still starting his career as a detective.

"Criminal Minds" season 12 returns tonight on its usual timeslot, 9 p.m. ET, on CBS.