Season 4
Season four's main mystery revolves around Juliet Sharp, a secretive girl with an agenda against Serena involving her past. The second half of the season builds on the complications of Serena's new found relationship with her former teacher Colin, Chuck trying to regain control of Bass Industries from Russell Thorpe, and Dan and Blair's growing friendship. The season also focuses on Lily's past betrayals coming back to haunt her; Chuck and Blair's tumultuous relationship after their break up; Dan and Vanessa's deteriorating friendship; and the arrival of Serena's cousin Charlie Rhodes to the Upper East Side. By the end of the season, Blair has ignored Chuck, Dan has told Vanessa they are no longer friends, and Serena is on that single grind.
Episodes
1 Belles de Jour Sep 13, 2010 
2 Double Identity Sep 20, 2010 
3 The Undergraduates Sep 27, 2010 
4 Touch of Eva Oct 4, 2010 
5 Goodbye, Columbia Oct 11, 2010 
6 Easy J Oct 25, 2010 
7 War at the Roses Nov 1, 2010 
8 Juliet Doesn't Live Here Anymore Nov 8, 2010 
9 The Witches of Bushwick Nov 15, 2010 
10 Gaslit Nov 29, 2010 
11 The Townie Dec 6, 2010 
12 The Kids Are Not Alright Jan 24, 2011 
13 Damien Darko Jan 31, 2011 
14 Panic Roommate Feb 7, 2011 
15 It-Girl Happened One Night Feb 14, 2011 
16 While You Weren't Sleeping Feb 21, 2011 
17 Empire of the Son Feb 28, 2011 
18 The Kids Stay in the Picture Apr 18, 2011 
19 Petty in Pink Apr 25, 2011 
20 The Princesses and the Frog May 2, 2011 
21 Shattered Bass May 9, 2011 
22 The Wrong Goodbye May 16, 2011