This takes place near the end of the movie, when William Wallace has been captured and thrown in jail. Princess Isabelle then decides to pay him a visit and they talk for a few minutes. She is let in by a prison guard, who leaves the room soon after she enters.

During this scene if you look at the door to the prison cell, which the prison guard leaves a bit open, you will notice that it's open widely in some shots and that it's almost closed in other shots even though no-one touches the door in between. In one of the shots the shadow of the prison guard can be seen but it disappears shortly after.