The Flash -- "Flash vs. Arrow" -- Image FLA108a_0311b -- Pictured: Tom Cavanagh as Dr. Harrison Wells -- Photo: Katie Yu/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108c_0009b -- Pictured: Jesse L. Martin as Detective Joe West -- Photo: Diyah Pera /The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108a_0459b -- Pictured: Danielle Panabaker as Caitlin Snow -- Photo: Katie Yu/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108c_0024b -- Pictured (L-R): Grant Gustin as The Flash and Jesse L. Martin as Detective Joe West -- Photo: Diyah Pera /The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108a_0595b -- Pictured: Emily Bett Rickards as Felicity Smoak -- Photo: Katie Yu/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108c_BTS_0044b -- Pictured (L-R): Behind the scenes with Director, Glen Winter -- Photo: Diyah Pera/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108b_0053b -- Pictured: Stephen Amell as Oliver Queen -- Photo: Diyah Pera/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108c_0157b -- Pictured (L-R): Grant Gustin as The Flash and Stephen Amell as The Arrow -- Photo: Diyah Pera /The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108b_0124b -- Pictured: Grant Gustin as Barry Allen -- Photo: Diyah Pera/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108c_0215b-- Pictured: Grant Gustin as The Flash -- Photo: Diyah Pera /The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108b_0147b -- Pictured (L-R): Grant Gustin as Barry Allen and Stephen Amell as Oliver Queen -- Photo: Diyah Pera/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108c_0229b -- Pictured: Stephen Amell as The Arrow -- Photo: Diyah Pera /The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108b_0294b -- Pictured (L-R): Grant Gustin as Barry Allen and Stephen Amell as Oliver Queen -- Photo: Diyah Pera/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108c_0195 -- Pictured: Grant Gustin as Barry Allen and Stephen Amell as Oliver Queen -- Photo: Diyah Pera/The CW -- © 2014 The CW Network, LLC. All rights reserved

The Flash -- "Flash vs. Arrow" -- Image FLA108b_0468b -- Pictured (L-R): Stephen Amell as Oliver Queen/The Arrow and Grant Gustin as Barry Allen/The Flash -- Photo: Diyah Pera/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108a_0132b -- Pictured: Jesse L. Martin as Detective Joe West -- Photo: Katie Yu/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108b_0516b -- Pictured (L-R): David Ramsey as John Diggle and Emily Bett Rickards as Felicity Smoak -- Photo: Diyah Pera/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108a_0144b -- Pictured (L-R): Emily Bett Rickards as Felicity Smoak, Tom Cavanagh as Dr. Harrison Wells, Danielle Panabaker as Caitlin Snow, and Carlos Valdes as Cisco Ramon -- Photo: Katie Yu/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108b_0531b -- Pictured (L-R): David Ramsey as John Diggle and Emily Bett Rickards as Felicity Smoak -- Photo: Diyah Pera/The CW -- © 2014 The CW Network, LLC. All rights reserved.

The Flash -- "Flash vs. Arrow" -- Image FLA108a_0302b -- Pictured (L-R): Danielle Panabaker as Caitlin Snow, Emily Bett Rickards as Felicity Smoak, and Tom Cavanagh as Dr. Harrison Wells -- Photo: Katie Yu/The CW -- © 2014 The CW Network, LLC. All rights reserved.