"The Scientist" is the 8th episode of the second season of Arrow. It aired on December 4, 2013.
A seemingly impossible robbery at Queen Consolidated's Applied Sciences Division brings Central City police scientist Barry Allen to town. Citing a similar case back home, Barry offers to help Oliver and his team with the investigation. Oliver senses there is more to Barry than meets the eye, but he's distracted by the similarities between this current case and something that happened on the island. Meanwhile, Felicity takes a liking to Barry, which doesn't go unnoticed by Oliver. Sin asks Roy for help when a friend of hers goes missing. Roy is surprised when Thea not only encourages him to help, but joins the search. Unfortunately, Sin's friend is connected to Brother Blood, and their search ultimately gets one of them seriously injured.
- This episode introduces the character of Barry Allen, who in the comics (and later in the spinoff series The Flash) is the civilian identity of the Flash. This marks the first time a major hero from the comics is shown in the series.
- During the first scene involving Barry Allen, he can be seen holding a magazine questioning the S.T.A.R. labs particle accelerator's safety. Barry and Felicity later see a news broadcast on the same subject.
- This episode is notable as being the first episode of Arrow to hint at super-human abilities; previously the show was considered to be extremely grounded.
- In one shot, the name "Kord" was seen on lab equipment in a Queen Consolidated lab. This is likely a reference toKord Industries and Ted Kord.
- Barry mentions seeing a blur during his mother's murder; this references the archenemy of The Flash, known as Professor Zoom or Reverse-Flash, who in the comics kills Barry's mother exactly the same way. In The Flash, it is revealed this same person, Eobard Thawne, who goes by Reverse-Flash, is the murderer of Barry's mother.
- Lightning and thunder is heard while Barry is by the shelf holding chemicals. This is a reference to how Barry Allen, in the comics, got struck by lighting and was doused in chemicals, therefore getting his powers. A scene where Barry gets his powers in the same way will be seen in both the next episode and the Pilot episode of The Flash.