While Enterprise visits Earth for the launch of Columbia NX-02, Dr. Phlox is kidnapped by a band of Klingons who are desperate to find a cure for a genetically-engineered virus that threatens their entire race. Meanwhile, Trip begins his new assignment aboard the Starship Columbia as it prepares to embark on its maiden voyage and Reed's ties to a mysterious intelligence organization compromises his allegiance to Archer and Enterprise. Later, T'Pol attempts her first mind-meld in the search for clues to Phlox's whereabouts.

John Schuck (Dr. Antaak)
James Avery (General K'Vagh)
Ada Maris (Captain Erika Hernandez)
Eric Pierpoint (Agent Harris)
Terrell Tilford (Marab)
Kate McNeil (Commander Collins)
Brad Greenquist (Alien #1)
Derek Magyar (Commander Kelby)

Marc Worden (Klingon Prisoner)
Seth MacFarlane (Ensign Rivers)

• Part 1 of 2.
  
• Hoshi and Phlox finally visit Madame Chang's restaurant, which he cancelled earlier in the season in "Home".
  
• Reed is contacted by Harris, who is apparently an agent in Section 31, introduced in the DS9 episode "Inquisition".
  
• Hoshi is knocked unconscious defending Phlox from the kidnappers. Archer asks T'Pol to perform a mind meld with Hoshi to see if they can gather any clues. Since it's her first mind meld, Archer helps walk her through it.
  
• They discover the kidnappers spoke Rigelian, which leads them to a Rigelian freighter. They find the freighter destroyed and the crew dead. Weapon analysis shows it was Klingon disruptors, which Reed covers up. After Reed is caught in a lie and erases the Rigelian black box, Archer relieves him from duty and throws him in the brig pending court-martial.
  
• The virus was created by the Klingons using DNA from the Human Augments in trying to create a Klingon Augment. One of the test subjects had the Livodian flu and the virus mutated. They tried to get Dr. Arik Soong, but he was too heavily guarded, so they took Phlox instead.
  
• Admiral Gardner has replaced Admiral Forrest as the commander of the fleet.
  
• Kelby has been promoted and replaces Tucker as the Enterprise Chief Engineer.
  
• Hernandez has to remind Tucker to replace the Enterprise patch on his arm with a Columbia patch.
  
• Hernandez served on the Republic under Captain Jennings before she received command of the Columbia.
  
• Ensign Rivers (played by Seth MacFarlane) has apparently been transferred to Columbia.