The character and casting conventions of a thriller film/trailer are that they often consist of a battle between the protagonist character and the antagonist, when there is a disruption in the equilibrium. Then the story shows a chain of bad events building tension and suspense for the climax. The aim of the protagonist is to restore justice, while the antagonist seeks to destroy it. The protagonist is often a brave male who seeks to restore the equilibrium. The antagonist will have a hidden identity that the audience will uncover as the film progresses. Often the antagonist goes out for revenge from a past event. The storyline will be designed so the audience will think that it can happen to them, which will make them feel scared.
I looked at the casting conventions of particular films too see the conventions in casting a thriller film. For example in Kidnap, Alone and scared, Karla Dyson (Halle Berry) is unwilling to leave the fate of her son's life in someone else's hands. When she catches a glimpse of the abductors speeding away, she decides to fight back. In a heart pounding race against time, Karla begins a high speed pursuit and will stop at nothing to save her son's life. The casting of her character Halle Berry is well known in the Thriller genre for other films such as The Call which is about when a 911 operator takes a life-altering call from a teenage girl who has just been abducted, she realizes that she must confront a killer from her past in order to save the girl's life. This shows that she was chosen specifically in order to conform to the casting conventions of the thriller genre as the audience will recognise her from previous films.