Jean-Pierre Jeunet, the creative force behind “A Very Long Engagement,” has always been a quirky director. In fact, “quirky” is putting it mildly. His early films, “Delicatessen” (1991) and “City of Lost Children” (1995), often seem like illustrations for the definition of “postmodern” proposed by Moe Sislak of “The Simpsons”: “weird for the sake of weird.”

But with “Amelie” (2001) he seemed to find a style and a star that not only suited him but that produced an enormous popular success. It made more money in France than any French movie ever had before. The style was one of postmodern whimsy joined to a sweet but sentimental love story that reached beyond itself to look as if it meant to put the whole world to rights. The star was the lovely and lovable Audrey Tautou.

Now he is back again with the same style and the same star and an equally enjoyable romp. Ms. Tautou is made even more adorable by being an orphan and having a limp, caused by polio. Mr. Jeunet even takes up the same theme, namely the power of the love of two attractive young people to change the world – or at least the magical, weird-for-the-sake-of-weird world he is at pains to create here.

There are some of the same problems, too, most notably the near epic scale of the canvas on which he is working, which comes across as being too crowded, too confused with incident and characters who would be interesting in their own right but seem too distantly related to the main story. Most importantly, more than “Amelie,” “A Very Long Engagement” cannot avoid an eventual collision with reality.

Mr. Jeunet seems deliberately to court this collision by beginning in a World War I trench on the Western front as five French soldiers are being led forth to execution. You don’t get much more real than that. In fact, I would say that the common view of “reality” as something sordid and horrifying, which lurks beneath pleasing but deceptive appearances, arose out of these trenches.

Each of the five men has been sentenced to death for self-mutilation in a desperate attempt to escape from the hell of war at the front. As they are led through the trench to what is meant to be their final hour, Mr. Jeunet gives the back-story of each, and how he came to this unfortunate pass in a trench with the weird name, even in French, of Bingo-Crepuscule.

The most poignant and memorable of the men is the still-boyish Manech (Gaspard Ulliel) from Brittany, also known as “bleuet,” or “cornflower,” as the increasingly young draftees were called late in the war. He has gradually had his wits turned by the horrors of the war, and he finally snaps as a friend next to him is blown to pieces by a shell, the pieces ending up all over Manech.

The men are sent forth into no-man’s land, which all recognize as a certain death sentence. Thus, for the sake of their families, they may be listed as killed in action. But when the word comes home to Manech’s young fiancee, Mathilde (Miss Tautou), she doesn’t believe it. So strong is the psychic bond between them, she believes that if Manech were dead she would know it independently.

So after the war she sets out to find him, or at least to find out what happened to him, with the help of an influential friend (Andre Dussollier) and a private detective she hires herself (Ticky Holgado). She learns of the rough justice meted out to Manech at the front, but she looks in vain for anyone who can confirm his death.

The search, however, entangles her in the backstories of the other four men as well as two others who were present in Bingo-Crepuscule on the fateful day. All these strands of narrative are woven together to produce such a shaggy-dog story that Mr. Jeunet even includes a shaggy dog with gas problems as if to confirm it.

For American viewers, the most memorable thread in the tapestry may be provided by Jodie Foster – her accented French is attributed to her being Polish – as a military wife who sleeps with another man in order to get pregnant, in order to get her husband sent home from the front, and who thus finds love, or at least sensual delight, for the first time.

Another director might have found enough material for a movie just in this vignette, which takes up about 10 minutes’ worth of Mathilde and Manech’s story, in spite of being only tangentially related to it. But Mr. Jeunet is a prodigal with his narrative materials and prefers to shoot off in a dozen different directions at once, perhaps as a way of suggesting the largeness of the central episode, and its significance beyond itself.

And this is where reality, and not just the conventional reality of trench warfare, really does come into it.

All the various subplots, each with its own bizarre touches, help to create for the main story of Manech aime Mathilde a sense of “magic realism” whose purpose, I take it, is to prepare us for something wonderful, if not quite miraculous, in the denouement. But I find that it has the opposite effect. The excess of extraordinary and original imagery earlier in the film detracts from the emotional impact of what ought to be an even more extraordinary conclusion, rather than adding to it.

Still, the lush excess of cinematic sweets does keep our attention for more than two hours and, together with the ever-adorable Ms. Tautou, makes this a movie worth watching.