French Lawyer Michel Boullard (Charles Boyer) is estranged from his cold and prudish psychiatrist daughter Lauren (Leslie Caron) – a 30-year-old virgin who is engaged to card-carrying wimp Arnold Plum (Dick Shawn).
Convinced his daughter is an old spinster at 30 and impressed by wealthy American oilman and notorious womaniser Paul Chadwick (Rock Hudson), Boullard asks Paul to seduce his daughter and make her realise what she’s been missing all her adult life – the “very special favour” of the title.
Paul poses as Lauren’s patient, telling her that he is irresistible to women and that he is too afraid to turn down a woman because it led to one committing suicide in the past.
The relationship between the two is strictly professional until they go out to a restaurant where Lauren tries to prove he can enjoy a night out without worrying about women flirting with him.
Lauren passes out from drinking too much champagne and Paul takes her back to her hotel and creates a scene, which makes it looks as if they have slept with each other. Lauren later learns that the setting was staged.
Reconnecting with his daughter, Boullard works with Lauren to exact revenge on Paul. The subterfuge involves inventing a lover for Lauren – a bullfighter named El Magnifico – and convincing Paul he’s lost his touch in the sack.
Paul catches on and enlists a female friend – switchboard operator Mickey (Nita Talbot) – to impersonate a man so that Lauren will think he’s now gay.
Lauren races to the hotel room where Paul and his “male friend” are to do the deed, sacrificing all to save Paul from the love that dares not speak its name.
The film ends with Paul and Lauren happily married, with several children underfoot and another one on the way.
Dr Lauren Boullard
Harry the Taxi Driver
Mickey the Switchboard Operator
Frank De Vol