Girls have been toting guns in anime shows almost from the moment that someone thought to sequence drawings to produce motion. Phantom isn't out to add anything new to the genre; hoary as it is, that'd be a tall order. But it is produced by Bee Train and directed by Kōichi Mashimo, a pairing that has been shaping girls-with-guns series into glacially hypnotic mysteries ever since they struck boob tube gold with the perennially popular Noir. They're veterans at what they do, and with more budget to fiddle with than usual (it is based on the popular visual novel from Nitroplus after all), they've produced a beautiful, slowly engrossing and occasionally surprising anti-action action anime.

As the anti-action descriptor suggests and as is par for Bee Train/Mashimo collaborations, the series moves like a sedated snail. The action comes in short, cinematic bursts between lengthy build-ups, repeated flashbacks aren't uncommon, and entire episodes pass while the series does little more than bleed atmosphere. The first seven episodes are basically one long, patient wind-up to the events of episodes eight through ten, which are themselves telling in that they spread the mid-season climax over three entire episodes. It's an approach that has destroyed series in the past (the stillborn Tsubasa for example) and will inevitably alienate less patient viewers, but it actually suits Phantom's doomed relationships and double-crosses quite well. And when the payoff comes, its boldness is all the more shocking for the reserve that preceded it.

Watching Ein and Zwei carry out elaborate assassinations while slowly reacquainting themselves with feelings that had been destroyed by their murderous conditioning has its pleasures, but Phantom only really comes into its own in episodes eight, nine and particularly ten, when events force Zwei into a tragic course of action that ultimately shifts the direction of the series altogether. The unexpected leap forward injects some much-needed energy into the series and finally shakes some real personality into the reticent cast. The grown Zwei of later episodes is an ice-cold assassin with a heart of deeply wounded romanticism—infinitely more appealing than the insecure amnesiac of the early going—and even one-note characters like Lizzie and Claudia take on complementary extra dimensions. It also leaves the series in a far more interesting place than it started out in. Zwei's new position in Inferno opens up a plethora of possible plot routes (for all their air of creeping mystery, Phantom's early episodes had only one way to go), while the embryonic bond between Zwei and street waif Cal is rife with interesting new emotional possibilities.

Mashimo fills his deliberate tale of assassins in search of their humanity with images of eerie beauty. His assassins pose themselves as string puppets, wear masks that turn their eyes into expressionless wells in white porcelain, and blend into shadows as if to the night born. Bee Train's world-class backgrounds bring the series' decaying warehouses, sanitized urban interiors and neon jungles to vibrant life, while the clean, no-nonsense character designs spend most of their time looking simply great. Together the visuals create a nebulous aura of cold dissociation that complements perfectly the cold calculation of the plot, while making Zwei's little islands of warmth (Ein, Cal) seem fragile and precious in its frigid grip.

Mashimo keeps his penchant for endlessly panned stills under wraps, preferring quick movements and judicious use of slow motion for his brief, swift action scenes. Active scenes are rare though; the quality of the series' animation is better judged by noting the subtlety he imbues the expressions and movements of his characters with. Ein's heartbreak at turning Zwei into a monster can be read clearly in her reactions to his flashes of killer instinct, just as Zwei's un-partner-like regard for her can be read in the way he looks at her. Subtleties like that don't come cheap.

Hikaru Nanase composes Phantom's score in the style of long-time Mashimo collaborator Yuki Kajiura. It's a remarkable homage, mixing classical instruments and arrangements with electric guitars and synthesizers to create the kinds of creepy musical textures that Kajiura is known for—but without the baseball-bat-upside-the-head bombast that often mars Kajiura's work for Mashimo. The otherworldly opening by KOKIA, by the by, ranks among the years' very best.

It could do with some defibrillation and maybe a sense of humor, but Phantom is probably Kōichi Mashimo and Bee Train's most successful series in years. A solid plot and a well-hidden romantic heart combine with Mashimo's vaguely supernatural atmosphere to create something that, while not brilliant, is involving and interesting and looks great, with the promise of more, and possibly better, to come.