Christmas 1975 and Queen's Bohemian Rhapsody is riding high in the charts. In a residential street just outside Cardiff a loud knocking breaks the stillness of the evening. When Rob Parsons, a young lawyer, opens his door, he finds a homeless man standing before him, clutching a bag of belongings and a frozen chicken. Rob and his wife Dianne invite Ronnie Lockwood into their home, cook his chicken and offer him shelter for the night. What happens next is an astonishing story of human kindness, self-learning, incredible pain, unbelievable hope and the sheer power of love to change a life. 'A Knock at the Door' is the true story of this homeless man who entered the home of a young couple, became a dustman and lived as part of their family for over forty-five years until his death.