Last week I wondered why Nate forgot to he is mad at Serena. This week I got my answer: Nate's still in love with her! Dan came to Nate for advice on how to deal post-threesome with your best friend and your girlfriend because of Nate's expertise in love triangles (Nate: I know things. I've been to Europe. Chuck Bass is my best friend), while Serena came to Nate for help with not sleeping with his cousin, a married congressman (Nate's also a professed expert on affairs with married people). Nate decided the best way to deal with Serena was to watch her every second, including a pub crawl that involved confessing his former (?) love for her. Apparently Serena never realized the depth of Nate's feelings after she stole his virginity and his shirt and went off to un-kill a dude. Unfortunately Serena went off with his cousin after all that, but it looks like that triangle comes to a head next episode (sadly, we have to wait until the 30th).
More importantly, though, Nate is so forgetful that even when Serena goes off to do the exact thing that he was mad at her about to begin with (potentially ruining his family's congressional reputation), he can't even remember to try to stop her, instead focusing on drowning his sorrows. Good work, Nate!