Pleasant and predictable are the words that best describe Miss Pettigrew Lives for a Day, Bharat Nalluri's adaptation of a 1938 novel revolving around an unemployed middle-aged English governess' whirlwind one-day spell as guardian angel for a dizzy American singer.

What saves the day for Miss Pettigrew from its vaudeville start, however, is the way the screenplay adds a sense of humanity to apparently two-dimensional characters, assisted by measured performances from the film's stalwart character-actor cast.

Frances McDormand (above left) is mesmerising as Guinevere Pettigrew, who at the beginning of the film is dismissed from her job and resorts to handouts from a soup kitchen near Waterloo Station. During an ill-fated meeting at her employment agency, she overhears a request from wannabe starlet Delysia Lafosse (Amy Adams; above centre) for a social secretary and seizes the opportunity by turning up at Lafosse's home, claiming to be the agency's recommended candidate.

What follows for the next half-hour is a Noel Coward-like satire about the horrid excesses and airy pretensions of London's social elite, as Pettigrew - a proud 'vicar's daughter' - witnesses with horror Lafosse's dishonesty towards her many suitors, including lounge owner Nick (Mark Strong) who bankrolls her lifestyle, rich daddy's-boy Phil (Tom Payne), considering who to cast as a lead in his first stab at being a theatre producer, and hard-up pianist Michael (Lee Pace), the true love Delysia seems destined to forsake in favour of fame and fortune.

Until Pettigrew gets a makeover from Delysia and her friend Edythe, an Anna Wintour-like style arbiter (Shirley Henderson; above right), Nalluri's film seems mired in farce, trading in sharp moves and even sharper lines that would come off better as theatre. It's when Nalluri slows the pace, revealing the fragile beings underneath the socialites' 'art of improvisation', that Miss Pettigrew becomes more emotionally engaging, giving meat to the line Delysia exclaims when hearing about Pettigrew's working-class British life: 'It must be extraordinary being you!'

It emerges that it's not only Pettigrew who is trading in deception for a living: Delysia - real name Sarah Grubb - is the daughter of a Pennsylvanian steelworker and she's as much a fish out of water as Pettigrew is in glitzy London. Joe (Ciaran Hinds), Edythe's middle-aged lingerie-designer fiance, also reveals himself as a frustrated individual caught in a world he can't bear, as he secretly struggles with his conscience, living a life of luxury but remembering how all his childhood friends died (like Pettigrew's late fiance) in French mud during the first world war.

It's from here that Nalluri delivers one of film's most poignant scenes, with Guinevere and Joe, the only two people at Delysia's party who have known vividly the horrors of war, sharing a moment of pained retrospection as British bombers roar overhead, foreshadowing the Blitz. 'They don't remember the last one,' says Pettigrew, to which Joe answers: 'No. They don't.'

With everything a period drama needs - the colours and the atmosphere of the 1930s, the affectations of the upper-class and the fears and anxieties of those anticipating a rerun of the Great War, but this time even much closer to home - Miss Pettigrew is a mix of charm and introspection whose poignant moments overshadow the prosaic romantic choices made by the protagonists.

Miss Pettigrew Lives for a Day opens today