The boy (spoiler)
If you were the boy (Ant), what you would do ?
It seems he has a lot of chance to escape as the evil couple doesn't really constraint him, even took him to a vacation abroad. He could for example give a secret note to the danish couple met in Italy, knowing that the couple is from denmark. This will definitely raise suspicion as why an english couple has a child who speaks danish. He could also run to a policeman while in town. Maybe he had done it before, and people/policemen just ignore it after the evil couple tell people that the boy had mental breakdown, or like to stir troubles