Dean Pelton lets two designers test their new social networking application at Greendale, leading to a war among the students; Professor Hickey decides to go underground until the battle ends.

Cameron feels competitive when a popular teacher returns from sabbatical; Haley goes to a realtor’s banquet with Phil; Mitch struggles to get his bearings at his new job; Jay and Gloria babysit Lily.

Brick makes it hard for Mike to relax during the vacation he was forced to take; Frankie is furious when she learns that Axl was in town without letting her know; Sue tries extra hard to please her customers after receiving a bad review.

Oliver is shocked when he learns that Slade has come to Starling City. Back on the island, as Oliver, Slade and Sara prepare to take over the freighter from Ivo, Sara pulls Oliver aside and tells him he needs to kill Ivo to prevent him from telling Slade what happened with Shado. Oliver feels immense guilt over the situation but realizes Slade’s growing rage from the Mirakuru makes him unpredictable and he could turn on his friends if he thinks Oliver is to blame. Oliver agrees to kill Ivo and the battle begins.

Aaron awakes to find himself in a world with power, married to Priscilla and running his company. As he gets the feeling that something isn’t quite right, familiar faces begin to appear.

Coulson goes on the attack to save Skye–enlisting the aid of Ward’s former S.O. John Garrett and uncovers shocking truths about his own life and S.H.I.E.L.D.

Beckett is recruited to assist on a Narcotics investigation, but a routine mission turns deadly when an undercover operation goes awry. To survive, Beckett must engage in a battle of wits against some of the most dangerous men in the New York underworld – including a powerful enemy from her past.

On the morning of the wedding, Lily and Robin have a fight and Barney freaks out about which suit to wear. Meanwhile, the gang watches a movie Ted has forbidden them to see.

When an aggressive virus wipes out Gabriel’s memory, he thinks Jin Cong is good and helps him find a secret document.

Hart and Cohle call a truce to investigate a series of disappearances that may be related to the Dora Lange murder and the Tuttle family.