The film tells of how he was adopted by an elderly white couple in 1958 and brought up in Slade Green, an all-white area of London.
Cass is forced to endure racist bullying on a daily basis from local children, who also ridicule his feminine-sounding name, "Carol", a name given to him at birth.
So he creates cards with the infamous slogan, "Congratulations, you have just met the famous ICF", and gives a TV interview, increasing the firm's notoriety for humiliation, their speciality.
However, the government under Margaret Thatcher begins to come down hard on hooliganism, and after an organised attack on a group of Newcastle United supporters, Cass is imprisoned for four years.
In the following weeks, Cass is haunted by his demons after the shooting; he sees visions of his attacker, he can't sleep and on one occasion, makes a violent outburst at his son.