Here's what happens when a feud is so entrenched that both parties can't see past the ends of their noses. The Tellarites have had bad blood with the Andorians for a long time. The episode begins with a summit that is to occur to talk some peace. Archer welcomes (sort of) the Tellarites on board (they've met before when Porthos peed on one of their trees and almost caused an interstellar incident). Meanwhile, it appears that these people have attacked Shran's ship, killing most of the crew. Enterprise answers the distress call and manages to get the few survivors on board, including his friend/enemy/whatever Shran. Of course, there's a powder keg on the ship. The weird thing is that neither side was responsible. It appears that the Romulans are the perpetrators. They have never posed a threat before but it seems are intent on preventing alliances. Things go badly as Trip and Malcolm and some of the Macos are on the Romulan ship investigating. The episode ends badly.
