"The Anniversary Party," written and directed by actors Alan Cumming and Jennifer Jason Leigh, is a striking triumph--an incisive, thought-provoking look at the questionable longevity of a marriage, set at their sixth-year wedding anniversary, following a year-long separation. The couple is fading thirtysomething movie actress Sally Therrian (Leigh) and her novelist husband Joe (Cumming), who is about to start filming an adaptation of one of his own books. The upcoming film project, widely known to be about Sally, is one that he is planning to cast 22-year-old ingenue Skye Davidson (Gwyneth Paltrow) in, much to the chagrin of Sally, who is hurt he didn't choose her, instead.

Set over the course of a 24-hour period, the first hour depicts the guests (all real-life friends of Cumming and Leigh) arriving. The varied group, all involved in the Hollywood industry, include recent Oscar winner Cal Gold (Kevin Kline) and his wife Sophia (Kline's real-life spouse Phoebe Cates); the Therrian's business manager Jerry Adams (John Benjamin Hickey) and his daffy wife, Judy (Parker Posey); Mac Forsyth (John C. Reilly), the current director of the romantic comedy Sally is making, and his neurotic, ultra-skinny wife, Clair (Jane Adams); and Gina Taylor (Jennifer Beals), Joe's long-time photographer confidante. The two outsider guests are the Therrian's next-door neighbors, Ryan (Denis O'Hare) and Monica Rose (Mina Badie), whom they have been instructed to grudgingly invite to avoid a possible lawsuit over their long-standing feud about Sally and Joe's barking dog. Also making an appearance, and causing Sally's true feelings to begin to rise to the surface, is Skye Davidson.

After the corny party games are played (the charades scene is pricelessly funny and genuine) and Sally and Joe open their anniversary gifts, the designer drug, Ecstasy, is introduced to the group as Skye's present. Their subsequent ingestion by everyone who decides to stay paves the way for the film's second hour. At first enjoying themselves and having a blast, Sally and Joe have various encounters with the other guests that makes them question their own relationship, with a secret that Sally has been harboring that may threaten to tear them apart forever.

Highly publicized to have been filmed in 19 days on the controversial digital video format, "The Anniversary Party" has a naturalistic flow to it that makes it feel less like a fictional motion picture, and more like a two-hour eavesdrop on the type of party that the rich and famous might really throw. Adding to the realism is a flawless cast who, in many cases, play characters decidedly similar to themselves, and who all believably seem like a large gathering of good friends. Kevin Kline (1999's "Wild Wild West") and Phoebe Cates (who has not been onscreen since 1994's "Princess Caraboo"), for example, play a movie star couple who, in Cates' case, has given up her prospering film career to raise her children. Likewise, Jennifer Jason Leigh plays someone not too far away from where she herself is at--a woman in her late-thirties whose career has recently been on a down slope, questionably because she is now a little too old to be playing the "young" roles, and not old enough to be getting the Susan Sarandon or Meryl Streep parts. The screenplay, by Leigh and Cumming, is so very impressive that it actually seems more like a delightfully well-acted, two-hour improv, rather than a "written" piece.

As previously mentioned, the cast is a top-notch smorgasbord of reasonably well-known talent. In a film that houses many standout performances, Phoebe Cates is superb and (in one truthful sequence) heartbreakingly funny; Gwyneth Paltrow (2000's "Bounce") gives her role of Skye, who most think of as dense and childish, several different character shades that expose her to be a little smarter than she looks; Jane Adams (1998's "Happiness") reaps comic gold as a new mother who is, to put it mildly, an obsessive parent, as well as an obsessive dieter; Jennifer Beals (1998's "The Last Days of Disco") is astoundingly assured in the best role she's had in ages; and Leigh's half-sister, Mina Badie (1994's "Mrs. Parker and the Vicious Circle"), is quietly poignant as a neighbor who doesn't seem to have the same stuck-up attitude as her husband, and begins to realize their extreme differences as the night presses on.

The movie wouldn't be complete without the audacious, passionate effort that Jennifer Jason Leigh (1999's "eXistenZ") and Alan Cumming (2001's "Josie and the Pussycats") have put into their directing debut, as well as their two central acting turns. Leigh and Cumming have rarely been better onscreen than they are right here, as a couple who do, indeed, love one another, but might not be secure enough in their own bodies to be able to survive each other's company. Best of all is a confrontation near the end, as they search for their missing dog, that is full of such pain, anger, and betrayal that it's almost difficult to endure.

It's clear that Leigh and Cumming put their entire heart and soul into the project, as they've not only crafted a comedic drama of surprising depth, but one of true emotional maturity. Very Altmanesque in its free-flowing treatment of the characters and story, "The Anniversary Party" is alternately so adept, so funny, and so powerful that it manages to stand on its own as a true original. It's easily one of the best American films of the year.