Angel: A Hole in the World

When Fred receives a mysterious sarcophagus in the mail, she opens it but finds that it contain a mysterious virus, one which immediately begins to infect her. Upon further investigation of this virus, Angel learns an ancient demon parasite called Illyria is the cause, and it is up to him and Spike to get the demon back to its rightful resting place before it consumes Fred and, potentially, many others.