Diggle and Oliver realize that Merlyn is helping Darhk with his escape plan. In the meantime, Laurel receives an unexpected proposal.
This is one of the most important episodes of Arrow and it's named Eleven-Fifty-Nine. As far as we now, Darhk is locked up and the Team Arrow handles the situation just fine. However, new information appears: Malcolm has a plan to release Darhk.
The team attempts to make Malcolm's plan fail but all the information they have is false. They fall into a trap and Malcolm gets what he wants. Oliver doesn't trust Andy at all and when the Team finally faces Damien, Andy betrays Oliver and the rest of the group. Before leaving, Darhk keeps his promise and reveals the mistery of season 4 first episode: Laurel is heavily attacked by Damien and she dies later at the hospital. This is definitely one of the saddest moments of the series despite Laurel wasn't one of our favorite characters. Now revenge is coming and nothing can stop it.
Interesting fact: the title of this episode, "Eleven-Fifty-Nine" is the exact moment Laurel takes her last breath.