When Dieter folds the newspaper and tucks it under his arm to lean on the fireplace mantel, the folded crease is facing up. In several following shots, the orientation of the folded paper changes from up to down and back.
When Harry Andrews (Inspector Mendel) and Lynn Redgrave (Virgin Bumpus) are talking in the theatre, Lynn Redgrave can be seen mouthing the last words of Harry Andrews' line before she speaks, revealing her technique for learning her lines.
When Charles Dobbs (James Mason) makes his second visit to Elsa Fennen there's a clear shot of the the street name, The Crescent, on a front wall by the house. Later he gets a colleague to send a postcard to Elsa and tells him that the address is Merrydale Lane. The next scene shows her coming out of the house and another clear shot of the street name, The Crescent.
Harry Andrews and Simone Signoret get on a London bus outside the Victoria Coach Station. An upstairs shot looking to the back window shows the bus leaving Trafalgar Square and going down Whitehall and is then seen stopping outside the Aldwych Theatre at the far end of the Strand.