Take a look at the episode description and some promotional photos for the next episode Whitney, "The Wire".
In episode 5, after an argument over whether or not Alex uses a condescending "tone," Whitney decides she is going to catch her boyfriend in the act and enlists Mark's help. The two scheme to set up a hidden camera in the couple's apartment. Lily, Roxanne and Neal gather around the television to watch the drama unfold. Later, Alex's brother Brian crashes on the couch, and old sibling rivalries come to the surface causing the two brothers to brawl.