At its opening, Magi is classical adventure, a tale of magic and derring-do set in the fantastical world of Hollywood's Arabia. In the first episode Alibaba and Aladdin meet in a cutthroat marketplace, bond at a brothel, and beat the tar out of a mustachioed villain straight from some Mideast variant of the Fu Manchu serial. It's wonderful. You can clearly hear the echoes of things like 1940'sThief of Bagdad and stop-motion wizard Ray Harryhausen's sublimely silly Sinbad pictures throughout. They're there in Magi's dungeon rooms o' fire, in its shameless takes on classic adventure tropes like the bazaar brawl and treasure-room showdown. But most of all it's there in the show's old-fashioned sense of adventure, where the world is a vast place of childlike wonder and danger, filled with the noblest of heroes and the vilest of villains; unexplored, unbounded; bursting with magic and mystery. Where a boy's turban can fly; where his best friend can be a Blue Giant with a flute for a head. Where caravans are menaced by booze-slurping carnivorous plants, and petty tyrants hold cruel sway over fierce warrior maidens. Watching is like being a kid all over again.

It can't last. And it doesn't. The headlong dash of the first episodes begins to slow once Aladdin and Alibaba move into the Dungeon. The series takes time out between raging fire traps and flame-spewing blob monsters to build up the back-stories of characters like Jamil, the evil young lord who chases Aladdin into the Dungeon, and Morgiana, his warrior slave-girl. Building character isn't a bad thing of course, but the first episode already proved that the series could do it—with Alibaba and Aladdin—without clunky retrospective interludes. In the meantime, the pair's journey moves away from Arabian Nights fantasies and towards something rather more video-game like, with mazes and traps and low-level beasties to fight. And then there are the rules. Rules are poison for a freewheeling adventure. Magic, we learn, is the province of Magi and Djinn. Magi are magicians whose role it is to choose rulers; Djinn are magical beings who rule over the Dungeons. Aladdin is clearly a Magi; Ugo, his blue headless friend, a Djinn. Rulers chosen by Magi capture dungeons and control Djinn, who give them power over elements like fire or wind. You can almost hear the series killing off its own possibilities, its previously boundless world closing up.

It isn't until the next arc, however, that Magi goes completely off the rails. The end of the Dungeon arc sends Alibaba and Aladdin off in separate directions, and the subsequent arc follows Aladdin as he falls in with a band of nomads clearly patterned after the ancient Mongols. They're in hard times and on the verge of falling under the control of an empire clearly patterned after feudal China. The band Aladdin finds himself in is led by a wise woman, who spends a great deal of time explaining Aladdin's magic and dropping clues about his origins and fate. When an imperial Princess and her nasty vizier enter the picture, talk turns to peace and war and the things proud people must do to survive in less prideful times. It is, in stark contrast to even the slower parts of the Alibaba/Dungeon arc, quite dull. The jawing slows the pace and keeps action at bay, the characters are simple and uninteresting, clearly doomed to their single two-episode arc, and the whole thing has little impact on Aladdin's life.

Still, you can't count the show out. You never can. For all its flaws, the Dungeon arc still manages to pull off a humdinger of a climax, complete with old-school duel (between Alibaba and Jamil) and a final dungeon level full of awe-inspiring magic and half-revealed mysteries—including a fabulously grumpy Djinn dungeonmaster. The nomad arc somehow yanks a thrilling battle from its rear, ending in the most satisfying way it can (and, not coincidentally, introducing another—this time amusingly naughty—Djinn). Episode six catches up with Morgiana, and builds via another of the show's pummel-worthy villains to a fantastic fight between kickass Morgiana and a small army of saber-tooth tigers. Every time you think that the series has lost its mojo, it does something that rekindles the adventure, waking that inner kid once again and dragging the outer adult along for the ride.

Koji Masunari is a director who prefers mobility to precision. His previous works—especially R.O.D. the TV and Kamichu!—were fluid works that emphasized expressive faces and the movement of bodies, whether they're lounging around the house or kicking bad guys in the head. There's a certain amount of that in the believable physicality of leg-strong Morgiana and in the sometimes complex ways that Toshifumi Akai's simple characters move. But Masunari is clearly working on a smaller budget here. His fights are cogent and effective, but rely as much on the force of the story as the thrill of their visuals for impact. Characters express themselves less subtly and less with movement than with how they're drawn. It doesn't help that Akai is no Taraku Uon or Takahiro Chiba. His designs are fun, especially when they lapse into goofy humor—which Masunari does very well—but they're also unexciting and have big, sappy smiles that Masunari uses way too much.

Instead, Magi is most memorable when spectacle is its focus. The top floor of the Dungeon is an eye-opener, the settings of all three arcs beautifully realized, and the magic flashy and fun. Ugo's emergences—flowing impossibly from Aladdin's flute like some sentient mass of congealing blue taffy—are particularly impressive. As are his Djinn comrades, whose frightening, elaborate beauty puts the human designs to shame.

As is his wont, Shiro Sagisu's score is an attractive, professional affair. It has the requisite faux Middle-Eastern flair, and enough rock fire and classical introspection to cover all the series' basic moods. It may not stand with his most touching or exciting scores, but it's good work nonetheless and occasionally considerably more than that. Which is as good a way to sum the show up as any. Likely it'll never achieve greatness—not even the greatness associated with Harryhausen's camp classics—but every once in a while it reaches heights to match the greats. It's just too bad it can't seem to maintain them.