Johan casts his black shadow over all of Monster, but the Frankfurt arc is definitely where his shadow is darkest and his presence most tangible. This is Johan's arc, the one where we get closest to the monster and delve furthest into its ambitions and inner workings. What we see there is terrifying.

Johan is a monster, a force of evil as elemental as wind or waves. Evil infects the children he tutors as surely as radiation poisoning effects children who cuddle up with plutonium: they warp, nihilism sprouting in the wake of his words like evil flowers after a desert rain. One can't help feeling sorry for the vulgar prostitute who tries to blackmail him in a later episode. Her confidence in the power of her petty human evil is pitiful in the face of the cold, implacable forces we know to be brewing beneath Johan's civilized exterior. Upon exiting his meeting with the prostitute, Johan plants seeds of destruction amongst the alley prostitutes as easily and casually as a pedestrian might litter. When something finally does shatter that unnatural calm of his, the link between the cause and the effect is so alien that the breach is more mystifying and frightening than humanizing. Johan himself says it best when discussing the incident with the doomed prostitute: "I thought I had reached the darkest place. But beyond that I saw an even blacker darkness." That could just as easily be us, peering further into his head.

Of course, the Frankfurt arc doesn't spend all of its time studying Johan. The cat-and-mouse game between him and Tenma heats to boiling here, eventually carrying the arc to its frantic, hellish conclusion. This is probably as blatant as the series' existential struggle between good and evil gets: two men, one the essence of decency, the other an avatar of evil, face off in a contest of wits and will from which only one can emerge intact. The show puts its own little morally ambiguous spin on it—in order to defeat evil, good must commit evil—but otherwise this is pretty unabashedly biblical. Heck, the bible even gets quoted. If moral struggles aren't your thing, the chase also offers up some terrific tension and even a couple of fine, spare action scenes. Granted it wades through quite a few short-stories about troubled children, teenaged underworld doctors, and Lunge being Lunge to get at them, but they're solid stories all and rarely dissociated enough from the plot to qualify as filler. Plus, once Tenma is in place and Johan's plan explodes unpredictably into action as the good doctor's crosshairs settle and you scream for him not to pull that trigger, gripes about pacing vanish in a puff of exhilaration. On a purely visceral level, episodes 37 and 38 are as good as the series has ever been.

Monster loves its twists, though, and Tenma and Johan's confrontation unfolds in strange and unexpected ways, eventually yanking the plot around ninety degrees and sending it loping off in an entirely new direction. That means, in the great Monster tradition, that the main players vanish into Europe's underworld and a whole new cast shuffles onstage to replace them. This is one of those habits of Monster's that will drive some people nuts. If you can't make peace with it and just accept the new story on its own merits, then you may want to take this chance to bail. This is not the last time that the series makes such a move, and it'll only drive you battier as the show wears on. Those who can, on the other hand, will be rewarded with an intricate espionage thriller that taps into a deep well of pulp cynicism about the dirty, ugly things that happen in post-Communist Eastern Europe. It boasts a fine, complicated lead in the haunted, perpetually smiling Grimmer, a vulnerable victim in upstanding rookie detective Jan Suk, plenty of betrayals, double-crosses and conspiracies, and more twists and turns than an epileptic snake at a laser show. And eventually, as everything does, it all leads back to Johan... and Tenma.

The action of the Frankfurt arc offers Masayuki Kojima a chance to show off a little, and he seizes it with a properly reserved enthusiasm. Johan's "breach" is shot as an epic dolly-in, computer-assisted camera spins add surreptitious flash to a cliffhanger showdown, and the death of one major character has the slo-mo clarity of a traumatic memory—which it soon becomes. His vision of Johan's endgame is one of the better animated approximations of hell on earth, and his handling of the subtler aspects of Urasawa's creative vision—the omnipresent atmosphere of unease, the timing and delicate execution of those moments when the larger picture jumps into focus—is persistently adept, if not inspired. The move to Prague highlights the stellar quality of the background art, which beautifully captures the forbidding magic of a place that characters regularly refer to as a "fairytale town."

Amidst all of that functional beauty and tasteful showboating, it can be easy to lose sight of the humbler aspects of the series' execution. Though not flashy, the character designs are thoughtfully illustrated and animated. Johan's overpowering presence has as much to do with his perfect, imperturbable posture and the facile emptiness of the amiable mask he wears as with his actions, and Tenma's predicament is plain to read in the sad kindness of his eyes and the determined set of his jaw. In the meantime the dissonance of Kuniaki Haishima's score works tirelessly in the background to keep us nervous and off-kilter—most effectively I might add.

Abrupt shifts and short-story inserts mark this run of episodes, as does the show's usual icy deliberation. Viewers displeased with any of those will be no more pleased with them now that the series has hit its second high-point than they were when it hit its first or any time in between. To them I say phooey. It cannot be overstated how brilliantly apart from the anime mainstream this unsettling, fiercely intelligent, and ultimately uncategorizable journey into darkness is. This is arguably the most successful stab anime has taken at mythmaking since Berserk, and for that alone it is essential viewing for anyone who is really serious about exploring the medium's capabilities.