After an armored truck is robbed, and the drivers killed, Oliver believes that one of the thieves is ex-marine Ted Gaynor, an individual from his target list. Diggle dismisses Oliver's assumption, as Gaynor was Diggle's commanding officer during his first tour of duty in Afghanistan and saved Diggle's life. Oliver goes after Gaynor regardless and steals encrypted data, but Diggle intercedes and prevents Oliver from getting any information directly from Gaynor. The data is revealed to be plans for robbing armored trucks, which Oliver uses to track and stop the thieves during their next heist. Oliver informs Diggle that Gaynor was not at the heist, but someone from his security firm was. While investigating, Diggle learns that Gaynor was the mastermind behind the robberies, and is forced to join Gaynor's team to recoup the money they lost on the previously failed heist. Diggle backs out of helping Gaynor, who attempts to kill Diggle in retaliation. Oliver arrives in time and kills Gaynor before he can succeed. Afterward, Oliver apologizes for not trusting Diggle more, citing his time of the island when his trust was violated by Yao Fei, who is revealed to have been working with Fyers all along. Meanwhile, believing her mother is cheating on Walter, Thea ingests a new drug, "Vertigo", and crashes her car while speeding. She is subsequently arrested by the police for driving while under the influence.