The CSIs must investigate when a party girl is injured and killed in a traffic accident.

Oliver returns to Starling City on Earth-2, where he encounters familiar faces while trying to decipher the Monitor’s mission. Meanwhile, Mia and William’s team clash with a new foe.

Oliver assembles a group of unlikely allies – Slade, Nyssa, Merlyn and Digger Harkness – to engage in an epic battle against Chase and his army.

Oliver wakes up to a life where he never got on The Queen’s Gambit. Robert and Moira Queen are alive and well. Laurel is his loving fiancée and their wedding…