An antagonist is the character who basically causes the problems in the story. They do not have to be a bad person, they just simply have to create the conflict for the protagonist, whether on purpose or accidentally.
Conflict as a literary device is the challenge faced by a character that provides tension within the story. It can happen between two characters, between a character and their inner demons, or even between a character and the environment.
Out of the events provided, the one that would result in a conflict is "Soon, the people of the house, aroused by the noise, awoke and cried out, 'thieves, thieves!'", as it narrates the encounter between the antagonists and the other characters that will add tension to the plot. If the characters did not wake up due to the noise, the thieves presence would not result in a conflict.
