Slade returns and asks Oliver for help in tracking down his son. When they learn Joe has been taken hostage by mercenaries, their mission to save him gets complicated by a terrible revelation that could shatter Slade's hopes of reunion forever. Meanwhile, Vigilante reappears in Star City.

Cayden James ups the ante by launching his plan to take control of every aspect of the city. Despite the scope of Cayden’s plan, Oliver is determined to foil it with just the Original Team Arrow – and without the aid of Rene, Dinah, or Curtis. But things get complicated when William is endangered as a result of Cayden’s handiwork.

Looking to expand his empire, Diaz and Laurel meet with The Quadrant, a coalition of mafia families who run national organized crime. Meanwhile, after Oliver’s recent decision, Felicity and Curtis double their efforts on building Helix Dynamics.