Arrow Season 2 Episode 15 : The Promise
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.