Spoilers below for the Criminal Minds episode titled "Spencer."
In Season 12, Criminal Minds has changed its traditional dark course in several ways, with the highly dangerous Mr. Scratch serving as a season-long antagonist. (Not to mention the lack of Thomas Gibson's Hotch to handle things.) Showrunner Erica Messer has teased another big shake-up in the form of a multi-episode serialized arc, and it all kicked off in a huge way during "Spencer," which put the fan-favorite genius Reid in the middle of a murder mystery that currently has him behind bars. Currently, as in, "he didn't get out before the end credits." Plus, it involved a crossover.
Fans knew that Reid was heading to the slammer from trailers and things, and it wasn't at all clear why; thought it also wasn't the most crazy concept, considering the normally clean-cut agent has had his hands full with his schizophrenic mother Diana, played by the always great Jane Lynch. And the arrest indeed had everything to do with her, as Reid was traveling to and from Mexico to meet with a doctor supplying him with experimental drugs he was using as a form of treatment. (That's what was up with the vials a few slaps, er, weeks back.) But the doctor, named Rose Medina, was found murdered, and Reid non-coincidentally has a distinct lack of memory about what went down, though he definitely remembers holding the knife that killed the doctor.
And so Reid gets charged for murder on top of the drug charges that landed him in jail in the first place. (He was found in a drugged-out haze racing after another vehicle headed toward the border, and he was hauling a trunk full of cocaine and heroin.) Thankfully, Reid won't be at the mercy of the Mexican court system, as Criminal Minds: Beyond Borders' Matthew Simmons (Daniel Henney) and Clara Seger (Alana de la Garza) joined Prentiss & Co. in order to clear things up on the international front, since not only is Reid an American citizen, but so was Dr. Rosa Medina.
And as it was stated earlier, the end credits appeared on the screen and Reid was still completely unshaven and in the custody of American authorities, with the real murderer(s) still a mystery, even though it looked like we were all in for a happy-ish ending. Viewers will actually get to see Reid going through the court process, complete with trial, as everyone at the BAU is presumably busting their asses to solve the case. The smart money is on Mr. Scratch being behind it all, since it should naturally be someone a villain so formidable who is given the chance to take Reid out of the picture for a while. But perhaps other surprises are in store. Maybe a Criminal Minds: Suspect Behavior crossover, for old time's sake?