The Scientist

When a superhumanly strong thief robs a Queen Consolidated warehouse, Central City police scientist Barry Allen comes to Starling City to investigate the case. However, despite his close working relationship with Felicity, Oliver suspects that there's more to the young scientist than meets the eye. Meanwhile, Sin asks Roy to help investigate the disappearance of a friend. In the past, Oliver, Shado, and Sara try to get Slade to the submarine so they can use the serum to save his life.

Caity Lotz

Sara Lance

John Barrowman

Malcolm Merlyn

Celina Jade

Shado

Summer Glau

Isabel Rochev

Graham Shiels

Cyrus Gold

Jennifer Cheon Garcia

Uniformed Officer

Jordan Schartner

Carl

Sheldon Trosko

Guard #1

Bex Taylor-Klaus

Sin

Dylan Neal

Dr. Anthony Ivo

Jesse Hutch

Officer Daily

Kevin Alejandro

Sebastian Blood / Brother Blood