Oliver (Stephen Amell) decides it's time for Thea (Willa Holland) to come back to Starling City, so he packs for Corto Maltese, where Felicity (Emily Bett Rickards) has traced Thea's whereabouts. Lyla (guest star Audrey Marie Anderson) asks Diggle (David Ramsey) to go with Oliver because one of her field operatives, Mark Shaw (guest star David Cubitt), has gone dark in Corto Maltese and she'd like him to look into it. Feeling responsible for Thea's departure, Roy (Colton Haynes) joins Oliver and Diggle on their journey. Shaw double-crosses Diggle, putting numerous A.R.G.U.S. agents, including Lyla, at risk. Meanwhile, Laurel (Katie Cassidy) meets Ted Grant (J.R. Ramirez), and Felicity adjusts to her new job.
