NGTV Guide: Monday, March 16

Gossip Girl is back! After weeks of reruns, we finally get to see what Chuck, Blair, and the rest of those crazy UES kids have been up to.

Gossip Girl – the CW 8/7c
“The Age of Dissonance” – The seniors put on a play, and Serena becomes attracted to the director. Elsewhere, Blair gets crushing news about her future; Dan and Rachel try to stay away from one another; and Chuck seeks help from his adversary, Carter Baizen (Sebastian Stan). Julian: Harmon Walsh.

Castle – ABC 10/9c
“Nanny McDead” – Castle and Beckett discover a young nanny dead inside a laundry-room dryer, and their investigation leads to a dangerous world of play dates. Meanwhile, Castle contemplates Beckett’s character while writing his “Nikki Heat” series.