While Henry leads the charge "unto the breach" (the giant hole they've just blown in the town's walls), Bardolph, Nim, and Pistol stay back and avoid the fray. (Hmm. So much for warfare turning these guys into noblemen.)
A Boy (who used to be Falstaff's servant and is conveniently named "Boy") says he wishes he were relaxing back in London at an alehouse. Pistol agrees that this sounds a whole lot better than fighting the French.
Captain Fluellen (a Welshman) shows up and screams at the men to start fighting, or else.
When Nim smarts off, Fluellen beats him and then chases after the men.
Alone on stage, the Boy tells us that Bardolph, Pistol, and Nim are cowards and thieves who've been roaming around stealing everything in sight. The Boy thinks stealing is unmanly and says he refuses to join in.
A note about the division of scenes: In some editions of the play, the action continues on in this scene. Other editions (like the Norton Shakespeare) end the scene here and continue the action in Act 3, scene 3.