★★★

A Simple Favour isn’t quite the dramatic shift from Bridesmaids director Paul Feig that its promotional scrawl might have you believe. For one thing, this is hardly the first time Feig has squeezed laughs into genre cinema – see also Spy and Ghostbusters.. Further still, it’s the comedy that flies here, leaving the mystery thriller, based on the book by Darcy Bell, firmly grounded. No, this really isn’t so far from Feig familiar.

Sizzling performers Anna Kendrick and Blake Lively lead the film, elevating an occasionally unlikely plot, as polar opposite mums whose quickly-formed bond ties them together in unpredictable ways. Kendrick is Stephanie, the do all, chirpy stay at home mother of Miles (Joshua Satine), who befriends classmate Nicky (Ian Ho), son of elegant, anti-mum Emily, played with vehement glee by Blake Lively. The stars prove to be an inspired pairing and sing in electric harmony.

Whereas Stephanie is a goofy mummy-vlogger who spends her time making friendship bracelets and sneaking vegetables into her son’s diet, Emily is the PR director of a high-end fashion brand by day and a martini downing, femme fatale by night. One decorated her home with her child’s drawings, the other with a lewd portrait of themselves, inspired by Courbet’s Origin of the World. By no right should these women get on, gifting screenwriter Jessica Sharzer free reign for delicious wit. Rejecting an early playdate invite, Emily barbs: ‘We can’t, mummy already has a playdate with a symphony of anti-depressants’.

Drawn together by their children and an increasing, mutual enthralment, it’s not long before the duo are drinking together and sharing juicy secrets from their darkest pasts. Then comes the titular favour, and it is simple: Emily asks Stephanie to pick up her son from school one night. Two days later, Stephanie still has Nicky and is beginning to worry about his missing mum. A further five days pass and she’s down right worried. Teaming up with Emily’s ex-writer husband Sean (a bland and thankless role for Crazy Rich Asians’ Henry Golding), Stephanie takes up the case herself. ‘As every mum knows,’ she tells her vlog viewers, ‘if you want something doing, do it yourself’.

Melding hints of Gone Girl with beats of The Lady Vanishes, Mother’s Day and The Devil Wears Prada, A Simple Favour is a tonal hodgepodge of a film, transitioning between genres with often uncomfortable instability. Smutty – frankly hilarious – gags about beavers in one scene are followed by the painful guilt of one character’s tragic past in the next. Before you know it, Feig’s segued to thriller, then cat and mouse mystery and back to comedy again. Such constant evolution would work better if each element were equally strong. Ultimately, whilst the comedy is sharp, the thriller is a touch blunt.

Stretches of plot progression drag, over-reliant on regular plot twists and, for too long, deeply missing the absence of Lively. In Emily’s absence, Stephanie’s darker underbelly is gradually unveiled but, in spite of Kendrick’s strong work throughout, it never really rings true. Likewise, the burgeoning romance between Stephanie and Sean is disappointingly skin deep, albeit still more convincing than his actual marriage to Emily. A failure to convince in the details is key to the film’s inability to entirely sell its overall arc. It’s not a bad story by any measure, just not the one you wish it were and know it could be in the hands of this cast and crew.

With its frothy French soundtrack, A Simple Favour works best when it’s having fun, which is most of the time. If the film’s darker notes feel a little light and thrills play off-key, this is, at least, Feig on fine comic form.

T.S.