The Harrises return to 10,000 B.C., determined to upload a virus that will stop all sinkholes, despite knowing that this will mean they will never get home again; an unlikely leader rallies the clearing to face an oncoming prehistoric threat.
Tracy decides to have a crew from a reality TV show follow him around, which Liz tries to use to her advantage. Plus, Jack decides to pre-record a benefit for a disaster that hasn't occurred yet.