Healthy Man

A pandemic of a mutated virus has taken over the world. The few who remained healthy hide in their homes. It would be crazy to go out on the street.
However...

 One old, lonely man in quarantine had too much time to think. The bitter man realized how much he despises his son. In fact, he is so disgusted that he decides to risk his own life to find a letterbox and send a message to him. This is the last opportunity to share hatred before humanity is extinct.