Supergirl -- "Medusa" -- Image SPG208b_0008.jpg -- Pictured (L-R): Melissa Benoist as Kara/Supergirl and Grant Gustin as Barry Allen -- Photo: Bettina Strauss /The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208b_0028.jpg -- Pictured (L-R): Grant Gustin as Barry Allen and Melissa Benoist as Kara/Supergirl -- Photo: Bettina Strauss /The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208b_0014.jpg -- Pictured (L-R): Melissa Benoist as Kara/Supergirl, Grant Gustin as Barry Allen and Carlos Valdes as Cisco Ramon -- Photo: Bettina Strauss /The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208a_0019 -- Pictured (L-R): Melissa Benoist as Kara/Supergirl and David Harewood as Hank Henshaw -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208a_0054 -- Pictured(L-R): Melissa Benoist as Kara/Supergirl and David Harewood as Hank Henshaw -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208a_0082 -- Pictured(L-R): Melissa Benoist as Kara/Supergirl, Helen Slater as Eliza Danvers, David Harewood as Hank Henshaw and Chyler Leigh as Alex Danvers -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208a_0086 -- Pictured(L-R): David Harewood as Hank Henshaw, and Chyler Leigh as Alex Danvers -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208a_0111 -- Pictured: Chris Wood as Mike/Mon-El -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208a_0113 -- Pictured: Helen Slater as Eliza Danvers -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208a_0120 -- Pictured(L-R): Melissa Benoist as Kara/Supergirl, Jeremy Jordan as Winn Schott, and David Harewood as Hank Henshaw -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208b_0064 -- Pictured: Melissa Benoist as Kara/Supergirl -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208b_0093 -- Pictured(L-R): Melissa Benoist as Kara/Supergirl, Chyler Leigh as Alex Danvers, David Harewood as Hank Henshaw, and Helen Slater as Eliza Danvers -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208b_0128 -- Pictured(L-R): Chris Wood as Mike/Mon-El, Melissa Benoist as Kara/Supergirl, Chyler Leigh as Alex Danvers, David Harewood as Hank Henshaw, and Helen Slater as Eliza Danvers -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

Supergirl -- "Medusa" -- Image SPG208b_0143 -- Pictured(L-R): Chris Wood as Mike/Mon-El and Melissa Benoist as Kara/Supergirl -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved

The Flash -- "Invasion!" -- Image FLA308a_0244b.jpg -- Pictured: Melissa Benoist as Kara/Supergirl -- Photo: Michael Courtney/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308a_0185b.jpg -- Pictured: Melissa Benoist as Kara/Supergirl -- Photo: Michael Courtney/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308a_0215b.jpg -- Pictured: Grant Gustin as The Flash -- Photo: Michael Courtney/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308a_0159b.jpg -- Pictured: Grant Gustin as The Flash -- Photo: Michael Courtney/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308a_0321b.jpg -- Pictured (L-R): David Ramsey as John Diggle, Willa Holland as Speedy, Melissa Benoist as Kara/Supergirl, Brandon Routh as Ray Palmer/Atom, Caity Lotz as Sara Lance/White Canary, Franz Drameh as Jefferson "Jax" Jackson and Dominic Purcell as Mick Rory/Heat Wave -- Photo: Michael Courtney/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308a_0048b.jpg -- Pictured: Melissa Benoist as Kara/Supergirl -- Photo: Michael Courtney/The CW -- © 2016 The CW Network, LLC. All rights reserved

The Flash -- "Invasion!" -- Image FLA308a_0339b.jpg -- Pictured (L-R): Willa Holland as Speedy, David Ramsey as John Diggle, Melissa Benoist as Kara/Supergirl, Caity Lotz as Sara Lance/White Canary and Franz Drameh as Jefferson "Jax" Jackson -- Photo: Michael Courtney/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308a_0399b.jpg -- Pictured (L-R): Caity Lotz as Sara Lance/White Canary and Franz Drameh as Jefferson "Jax" Jackson -- Photo: Michael Courtney/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308a_0494b.jpg -- Pictured (L-R): Brandon Routh as Ray Palmer/Atom and Willa Holland as Speedy -- Photo: Michael Courtney/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0012b.jpg -- Pictured (L-R): Victor Garber as Professor Martin Stein, Caity Lotz as Sara Lance/White Canary, Dominic Purcell as Mick Rory/Heat Wave, Franz Drameh as Jefferson "Jax" Jackson and Brandon Routh as Ray Palmer/Atom -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0046b.jpg -- Pictured (L-R): Stephen Amell as Oliver Queen, David Ramsey as John Diggle, Willa Holland as Thea Queen, Emily Bett Rickards as Felicity Smoak, Victor Garber as Professor Martin Stein, Caity Lotz as Sara Lance/White Canary, Dominic Purcell as Mick Rory/Heat Wave, Franz Drameh as Jefferson "Jax" Jackson and Brandon Routh as Ray Palmer/Atom -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0073b.jpg -- Pictured (L-R): Emily Bett Rickards as Felicity Smoak, Victor Garber as Professor Martin Stein, Caity Lotz as Sara Lance/White Canary, Dominic Purcell as Mick Rory/Heat Wave, Franz Drameh as Jefferson "Jax" Jackson and Brandon Routh as Ray Palmer/Atom -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0080b.jpg -- Pictured: Stephen Amell as Oliver Queen, David Ramsey as John Diggle and Willa Holland as Thea Queen -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0134b.jpg -- Pictured (L-R): Victor Garber as Professor Martin Stein, Caity Lotz as Sara Lance/White Canary, Dominic Purcell as Mick Rory/Heat Wave, Franz Drameh as Jefferson "Jax" Jackson and Brandon Routh as Ray Palmer/Atom -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0132b.jpg -- Pictured (L-R): Victor Garber as Professor Martin Stein, Caity Lotz as Sara Lance/White Canary and Dominic Purcell as Mick Rory/Heat Wave -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0162.jpg -- Pictured (L-R) Carlos Valdes as Cisco Ramon, Melissa Benoist as Kara/Supergirl and Grant Gustin as Barry Allen -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved

The Flash -- "Invasion!" -- Image FLA308b_0171b.jpg -- Pictured (L-R): Candice Patton as Iris West, Tom Cavanagh as Harrison Wells, Emily Bett Rickards as Felicity Smoak and Danielle Panabaker as Caitlin Snow -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0234b.jpg -- Pictured (L-R): Melissa Benoist as Kara/Supergirl and Grant Gustin as Barry Allen -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0258b.jpg -- Pictured (L-R): Tom Cavanagh as Harrison Wells and Emily Bett Rickards as Felicity Smoak -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0397.jpg -- Pictured (L-R) Stephen Amell as Oliver Queen, Melissa Benoist as Kara/Supergirl and Grant Gustin as Barry Allen -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved

The Flash -- "Invasion!" -- Image FLA308b_0401b.jpg -- Pictured (L-R): Melissa Benoist as Kara/Supergirl and Tom Cavanagh as Harrison Wells -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0440b.jpg -- Pictured (L-R): Dominic Purcell as Mick Rory/Heat Wave, Melissa Benoist as Kara/Supergirl and Franz Drameh as Jefferson "Jax" Jackson -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0445b.jpg -- Pictured (L-R): Melissa Benoist as Kara/Supergirl and Grant Gustin as Barry Allen -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0451b.jpg -- Pictured (L-R): Stephen Amell as Oliver Queen, David Ramsey as John Diggle and Willa Holland as Thea Queen -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308b_0493b.jpg -- Pictured (L-R): Stephen Amell as Oliver Queen, Melissa Benoist as Kara/Supergirl and Grant Gustin as Barry Allen -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308c_0143b.jpg -- Pictured: Grant Gustin as The Flash -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308c_0149bc.jpg -- Pictured: Grant Gustin as The Flash -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308c_0247b.jpg -- Pictured (L-R): Grant Gustin as The Flash and Stephen Amell as Green Arrow -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308c_0293b.jpg -- Pictured (L-R): Stephen Amell as Green Arrow and Grant Gustin as The Flash -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308c_0343b.jpg -- Pictured: Grant Gustin as The Flash -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308c_0412b.jpg -- Pictured: Stephen Amell as Green Arrow -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved.

The Flash -- "Invasion!" -- Image FLA308c_0466.jpg -- Pictured (L-R) Grant Gustin as The Flash, Stephen Amell as Green Arrow and David Ramsey as John Diggle -- Photo: Dean Buscher/The CW -- © 2016 The CW Network, LLC. All rights reserved

Arrow -- "Invasion!" -- Image AR508a_0009.jpg -- Pictured (L-R): Caity Lotz as Sara Lance/White Canary, Stephen Amell as Oliver Queen and David Ramsey as John Diggle -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved.

Arrow -- "Invasion!" -- Image AR508a_0100b.jpg -- Pictured: Caity Lotz as Sara Lance/White Canary -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved.

Arrow -- "Invasion!" -- Image AR508a_0137b.jpg -- Pictured (L-R): Katie Cassidy as Laurel Lance and Jamey Sheridan as Robert Queen -- Photo: Bettina Strauss/The CW -- © 2016 The CW Network, LLC. All Rights Reserved.