An old flame forks her way back into the life of a married man in Joshua Marston‘s mysterious and somewhat satisfying Complete Unknown. Marston struck a chord with debut Maria Full of Grace, which played Sundance 12 years ago, giving a drug mule a face in performer Catalina Sandino Moreno. With Complete Unknown, the Californian director harnesses a selfsame ability to craft complex female leads but allows the narrative to come to tatters as it crests its many tonal shifts.

We start with Rachel Weisz, a character we’re introduced to through her many trades and faces. A series of vignettes present a woman whose broad talents make her instantly suspect. She’s worked in a Chinese magic show, as a registered nurse, a Namibian biologist, a world traveler and a teacher – or at least that’s the story she’s sticking with. From go, she retains an opaque sense of danger. There’s something to her soft smiles and breezy gift of gab that register as untrustworthy, all accented by the fact that we visually see Weisz pouring herself into these many molds. Her character is urgently gripping, begging to be unwrapped.

Enter Tom, a successful economic strategist played with peculiar wonder by Michael Shannon. Wife Ramina (Azita Ghanizada) has a party waiting for Tom but when his colleague and close friend (Michael Chernus) shows up with a woman he recognizes (Weisz) now going by a different name, his life is thrown into prompt disarray.

The party – and the first act in entirety – has a great energy to it. Weisz’ obvious duplicity feels dangerous. The door is wide open for just about anything to happen. Instead, Weisz and Shannon end up rubbing Kathy Bate‘s bunions. #Don’tAskDon’tTell. Shannon shines in these early moments, casting knowing glances at Weisz but unable to make a move in front of his guests. A sense of turbulence permeates the opening scene, made all the richer by Tom’s inner circle’s apparent admiration of “Alice”. As he begins to process the unorthodox stylings of Alice, new territory with new pathways open up and both performers shine as they explore this new territory.

And much like Complete Unknown seeks to define the revolutionary notion of reinvention through Weisz’ Alice, the film itself reinvents itself at critical junctions. After the debut, Marston claimed his motive was to shift into a major left turn by the end of the first act and then left turn again in the home stretch. And while he claims the vacillating tone was intentional, it seems more like the tone got away from him. And that’s problematic.

As the film shifts from one stage to another, Marston trades in the currency of mystery for the ponderances of middle age. The pair walk through the twilight of New York City, commenting on their pasts and their presents. It’s reminiscent of a very particular other series that I’ll touch on shortly.

The enigma of Alice’s serial chameleon lifestyle is presented and resolved in a very matter-of-fact manner, snuffing out the inherent riddle that make the character – and the film – so intriguing in the first place. Even the idea of whether she’s making everything up, just weaving a fast-lipped fiction as she goes, is made concrete when Alice takes Tom to her lab where she’s studying a new species of frog that she had a hand in discovering – a thread that intentionally parallels her discovering new species within herself.

Then comes a scene spent with a few hundred leopard frogs that feels like Marston channeling all that pig business of Shane Carruth’s Upstream Color. But without the vagueness and strong-willed readiness to leave things up to interpretation. Which in turn comes on the heels of what feels like him aping Richard Linklater’s Before series where man and woman walk around reflecting on life. Again, the tone turns like he’s churning butter and the experience can be disorienting for the wrong reasons. For such an original setup, few original results percolate to the surface by its conclusion.

CONCLUSION: Like a meteor, ‘Complete Unknown’ shines bright early on but fizzles out when its evolving tone takes one too many left turns. The performances from Rachel Weisz and Michael Shannon are magnetic even when the structurally unsound narrative is not.