S01E19: Unfinished Business

When a young woman meets a violent death after partying at Verdant, Detective Lance and his new partner, Detective Hilton inform Oliver and Tommy that she was on the drug Vertigo. Oliver immediately pays a visit to the mental institution where The Count is locked up, but finds he is in no condition to deal drugs. However, when The Count escapes and Starling City is flooded with even more Vertigo-related violence, Oliver and Diggle make it their mission to track him down. After Detective Lance uncovers incriminating evidence against him, Tommy goes to great lengths to clear his name, and the fallout from his actions leads Tommy down a new, unexpected path. In a flashback to the island, Oliver recalls the lessons he learned from Slade and Shado.