Who is the Antagonist?

         In my novel, A Three Dog Life, the antagonist is the accident Richard experiences and the brain damage that he suffers. Once hit by the car on the busy New York City Street,  Richard survives the trauma of the accident but will never again be the same man. As his stay in the hospital comes to an end, Abigail is told about Richard's diagnosis and realizes that he can not come home to live. Instead, he is transported to a  rehabilitation facility. Richard's rehab does help him regain some of his motor movements, however the brain injury leaves him confused and disjointed. Abigail's  struggle is to come to terms with the reality that their life together as husband and wife is forever changed. The antagonist plays a cruel joke on this couple as Richard appears to be fine, however his confusion, anger, depression, fear, and anxiety will forever define and  determine his future. That single leash snapping in half, can be seen as the hand of the antagonist,playing out  Richard and Abigail's destiny.