We imagine that a particular person is the diamond thief. We presume that due to the characters wearing clean clothes and the sun is up in the sky, it is a new day. Although the above is particularly applicable to fictional narratives, it can be applied to many other forms and genres of film. In most documentaries , a story coexists alongside a plot as much as it would in a fictional narrative. We do not experience every single detail of a character or characters.
Protagonist is the term used for the lead character.