Contains full spoilers for this episode and earlier episodes.
Oliver arrives on Earth-2 to collect dwarf star particles for the Monitor, but the assignment brings him into a family he lost on his own Earth. Moira is alive and married to Malcolm Merlyn, while Tommy welcomes Oliver home. Their reunion has one painful absence: this world's Thea died from a Vertigo overdose. When Oliver breaks into Queen-Merlyn Enterprises, the particles have already been stolen, and the archer confronting him is Adrian Chase, this Earth's Hood.
Laurel stops the fight and explains that she and Chase protect Starling City together. Oliver suspects Malcolm of being the Dark Archer, only to discover Tommy beneath the mask. Tommy intends to destroy the Glades in revenge for Thea's death, using the stolen particles to power his bomb. Diggle follows Oliver from Earth-1 and persuades him to accept help. With Laurel and Chase beside them, they reach Tommy, and Oliver convinces him to deactivate the weapon.
In 2040, Mia, William, Connor and Zoe face a Deathstroke gang led by Connor's adoptive brother, J.J. A rescue mission saves the kidnapped Vasquez, but J.J. escapes with information he forced from him. Back on Earth-2, Oliver collects the particles and visits Tommy in custody. His chance to say goodbye to Moira ends as a wave of antimatter consumes the city. Oliver, Diggle and Laurel escape through a breach while Moira and Tommy disappear behind them.