arrow the scientist spoilers barry allen grant gustin flash cw 'Arrow' spoilers: 5 things to know about the Flash's arrival in 'The Scientist'

“Arrow” fans! The upcoming episode, “The Scientist,” introduces Barry Allen (Grant Gustin) — the man who will soon be known as the Flash. What’s coming in this excellent episode?

Check out five big spoilers here.

1. Barry Allen has a rather impressive entrance into the episode. It highlights just how much of a clumsy nerd this guy is — before he becomes a superhero anyway.

2. There have been few episodes of “Arrow” in which the events on the island and the events in the present-day parallel as perfectly as they do in “The Scientist.” Flashbacks in this episode are absolutely essential: Dr. Ivo’s work didn’t stay stranded on that island.

3. People who have been upset that “Arrow” doesn’t have enough comic-book themes like super-strength and pseudoscience will absolutely love “The Scientist.”

4. Felicity (Emily Bett Rickards) and Barry hit it off right away. Nerd calls to nerd, after all. Look for Oliver to have a very Oliver-ish reaction to the competition.

5. Having been exonerated of her crimes, Moira Queen does what Queens do best — she has a party. But is it a party without guests? (And no, Malcolm Merlyn is not invited.)

“Arrow” airs Wednesdays at 8 p.m. on The CW.