'House of Z' Review: Zac Posen documentary features the most emotional film moment of 2017

House of Z, the Zac Posen documentary currently playing at the Tribeca Film Festival, often feels like two movies instead of just one. At first, it's a family story, about the way wunderkind designer Posen was brought up among artists and incorporated mom Susan and sister Alexandra into his company. Arguably, the movie's emotional breakthrough point is when Posen calls his business breakup with his family "fucking messy" and sheds rare tears.

Then, almost suddenly, the movie morphs into the most high-stakes episode of Project Runway you've ever seen, focusing on Posen's preparation for his Fall 2014 show at New York Fashion Week. It's a critical show, serving as the comeback run for a designer who had lost his way. But this whole section of the movie seemingly has no connection to the family story that came before. It's like the stories of Posen himself and Posen the brand can't intertwine.

Then, for a brief, indelible moment, House of Z's two parts come together. What director Sandy Chronopoulos is trying to say about Posen, both man and designer, finally becomes clear. And it's all in the reveal of one dress.

Zac Posen at his Fall 2014 New York Fashion Week showFrazer Harrison/Getty Images

Chronopoulos, by her own admission in a statement provided to press, didn't set out to make a documentary about Zac Posen. She was making a TV special, but was jolted by something his sister Alexandra said after an interview: "Don't forget that Zac's story involves his family." The statement resonated with Chronopoulos, who went to Posen and asked about his family. His emotional response led to a refocusing, two more years of shooting and, eventually, Chronopoulos' first feature film.

This speaks to why House of Z feels bisected. A TV special became a biographical documentary, and it is painstakingly clear which parts were filmed before the change. Both parts are good, but they feel divorced. The most history lesson-esque sections, several about the way the 2008 recession affected the fashion industry, feel like they're telling instead of showing.

But one thread keeps coming up during the Fall 2014 show prep section of the film: the promise of one teal gown. It's a remarkable piece, inspired by the ceiling of the Guggenheim and constructed within an inch of its life. One of the newest members of Posen's atelier is doing the bulk of the work on the dress, but there's just too much to be done. Posen's partner, Christopher Niquet, worries there's no way the piece will be finished in time for the show.

This gives this section of the film a shape it might not ordinarily have. While it's exciting to see the first couple of pieces come down the runway, Chronopoulos interlaces the early footage of the runway with shots of the atelier workers frantically finishing the teal gown. When it finally does step out onto the runway, it's not just another dress, and it's not just a wow piece — it's a catharsis.

The teal dress as seen in 'House of Z' and Posen's Fall 2014 New York Fashion Week collectionJason DeCrow/AP

Pictures and even online video don't do the dress the justice that House of Z does. The reveal is filmed on an incredibly high-definition RED Epic camera, shot by cinematographer Vinit Borrison. The music, a song called "Fading Beauty" by Kenzo Bond, swells gorgeously.

The shot is devastatingly beautiful and quite literally breathtaking. It inspires gasps and tears. It is a marriage of story and filmmaking rarely seen in documentaries. If everything else in House of Z were merely fine — and much of it is far more than that — this shot alone would be worth the price of admission.

Chronopoulos' two films suddenly become one. The dress no one thought would be finished walks the runway. Posen, who struggled to come back from a fall, was in his finest form ever. All the pain of losing his family's involvement in the business, of taking a risk on a much smaller Fashion Week show than is expected; it all pays off in that one dress reveal. Even one of the less developed stories pays off: As Vogue's André Leon Talley notes, the gown served as a post-recession testament to the fact that glamour does matter.

The fact that Posen's company finally became profitable after that show is mentioned almost as an afterthought. It's nice to know, but once that teal gown came down the runway, it's clear Posen is going to be just fine.

As mentioned, there are other great moments in House of Z. Posen's breakdown when talking about struggles with his family and watching his staff walk out on him is compelling. The actual Fashion Week preparation segment is entertaining, well-edited and, again, pays off beautifully. Even if Chronopoulos' film doesn't quite thread every seam, there's so much beautiful work, it's hard to ignore.

But there's just nothing like that teal gown reveal. It's the most emotional, gripping cinema I've seen so far in 2017. In that moment, fashion, filmmaking and storytelling all come together to create something as beautiful as the gown itself is.

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