This episode is focused on a man who is caught trying to steal files from the X-Files by Agent Doggett. He gets arrested by Doggett and is brought in for question. He says that his name is Daniel Miller, but that is infact not his name, proven by Agent Doggett.
The majority of the episode is spent trying to figure out the identity of this severly burned man. But when he is proven to have injected an unknown metal substance into William, the story takes a turn.
During the episode, the man was identified as Agent Fox Mulder, but Skully does not think it is him. Later in the episode, his identity is revealed as Agent Spender, who was believed to be dead after being shot by his father.
This episode ended with William being adopted. In conclusion, this episode was very special. Probably the best of the series.