I saw part of a movie (or possibly TV drama) on TV in the 90s(probably).  English cast, set in 1940s period.  The scene I remember is 3 children (boys) wake up early and decide to go swimming without waking up any of the grown ups – they live in a big house with an outdoor pool.  They are playing with a ball in the swimming pool.  A man walks past with a newspaper and says morning to them, he then goes through a doorway in a hedge next to the pool (in my mind I keep thinking of a maze).  The boys lose their ball over the hedge and one of the boys goes to retrieve it.  He finds the man  who had passed them a short while ago has been knocked out and is unconscious.  The boys in the pool wait for his return with the ball – they get impatient because he has been gone ages and call out to him – he doesn’t reply but then the ball is silently thrown back over the hedge to them.  That is all I remember and I would really like to know what it was and how it all ended.  At the time it felt quite unsettling.  Thank you