The story takes place in Johannesburg, South Africa in 2016. In response to the rising crime rate, a large weapons company developed a fully mechanical police force. They mass-produced and put the mechanical police into use, achieving remarkable results in combating crime. As one of the developers, programmer Dean (Dev Patel) has been committed to creating a complete artificial intelligence robot. Until one day, his research made a breakthrough, but he did not get the support of his boss Michelle Bradley (Sigourney Weaver). Unwilling to fail, Dean secretly took a recently broken mechanical police out of the company, ready to perfect his research, but was hijacked by three gangsters halfway. Under the threat of the gangsters, Dean wrote No. 22 into a new system. No. 22 was reborn as "Chappie", and its birth is about to change the fate of many people...