Whimsical, wistful and studiously insubstantial, the new Woody Allen film is his most frothy since The Curse of the Jade Scorpion.
Yet it's not hard to detect beneath the surface the preoccupations of a comic film-maker who draws on Chekhov and Dostoevsky for inspiration.
Here he indulges his lifelong fascination with magic and illusion, while reflecting the understandable preoccupation of a man nearing the end of his eighth decade: is what we see all that there is?
Firth plays Stanley Crawford, a master stage magician in 1920s London who specialises in unmasking anyone who pretends to real mystical power: "It's all phony," he tells anyone who'll listen, "from the seance table to the Vatican and beyond."
When his old mate and fellow magician Howard (McBurney) alerts him to Sophie Baker (Stone), whose claim to clairvoyant power he has failed to debunk, Crawford's interest is piqued. Before you can say "more champagne?", they are installed in the Riviera villa of a wealthy American widow (Weaver) who is communicating nightly, via Sophie, with her dead husband.
To his consternation, Crawford can't find a fault in Sophie's shtick; worse, he begins to fall for her. And before the film's beautifully paced 97 mins are over, Allen has him - and us - wondering whether reality is simply the most persuasive of all illusions.
The mystery of Sophie's powers is of less interest here than the struggle the hard-headed man of science has with his most fondly held convictions about "the dull tragic reality of life".
Even when he pulls a metaphorical rabbit from the hat in the last reel, Allen's still saying "What if ... ?" It's not exactly Kierkegaard, but it adds a satisfying gram or two of gravitas to a featherlight entertainment.
The film runs a scene or two too long perhaps, but Firth and Stone are great together and the offhand allusions (the drive is from To Catch a Thief and the last scene tips a top hat to George Cukor's film My Fair Lady) add colour. And cinematographer Darius Khondji lends a magic light to landscape and interior alike - it's as pretty a movie as Allen's done in a while.
Eileen Atkins, Colin Firth, Emma Stone, Marcia Gay Harden, Hamish Linklater, Simon McBurney, Jacki Weaver, Erica Leerhsen, Catherine McCormack, Jeremy Shamos, Ute Lemper
Slight but deceptively deep