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The Flash -- "Cause and Effect" -- FLA321a_0021b.jpg -- Pictured (L-R): Keiynan Lonsdale as Wally West, Tom Felton as Julian Albert and Carlos Valdes as Cisco Ramon -- Photo: Jeff Weddell /The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321a_0029b.jpg -- Pictured: Carlos Valdes as Cisco Ramon -- Photo: Jeff Weddell /The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321a_0043b.jpg -- Pictured: Keiynan Lonsdale as Wally West -- Photo: Jeff Weddell /The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321a_0064b.jpg -- Pictured (L-R): Jesse L. Martin as Detective Joe West, Danielle Panabaker as Killer Frost and Carlos Valdes as Cisco Ramon -- Photo: Jeff Weddell /The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321a_0085b2.jpg -- Pictured (L-R): Keiynan Lonsdale as Wally West, Danielle Panabaker as Killer Frost and Tom Felton as Julian Albert -- Photo: Jeff Weddell /The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321a_0632b.jpg -- Pictured (L-R): Jesse L. Martin as Detective Joe West, Carlos Valdes as Cisco Ramon and Keiynan Lonsdale as Wally West -- Photo: Jeff Weddell /The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321a_0646b.jpg -- Pictured (L-R): Danielle Panabaker as Killer Frost, Tom Felton as Julian Albert, Candice Patton as Iris West, Jesse L. Martin as Detective Joe West, Carlos Valdes as Cisco Ramon and Keiynan Lonsdale as Wally West -- Photo: Jeff Weddell /The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0015b.jpg -- Pictured (L-R): Tom Cavanagh as Harrison Wells and Anne Dudek as Tracy Brand -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0028b.jpg -- Pictured: Anne Dudek as Tracy Brand -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0126b.jpg -- Pictured (L-R): Carlos Valdes as Cisco Ramon, Candice Patton as Iris West, Keiynan Lonsdale as Kid Flash, Grant Gustin as The Flash, Jesse L. Martin as Detective Joe West, Anne Dudek as Tracy Brand and Tom Cavanagh as Harrison Wells -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0161b.jpg -- Pictured (L-R): Keiynan Lonsdale as Kid Flash and Grant Gustin as The Flash -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0190b.jpg -- Pictured (L-R): Keiynan Lonsdale as Kid Flash, Grant Gustin as The Flash and Jesse L. Martin as Detective Joe West -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0233b.jpg -- Pictured (L-R): Anne Dudek as Tracy Brand and Tom Cavanagh as Harrison Wells -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0238b.jpg -- Pictured: Tom Cavanagh as Harrison Wells -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0261b.jpg -- Pictured (L-R): Candice Patton as Iris West and Jesse L. Martin as Detective Joe West -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0281b.jpg -- Pictured: Candice Patton as Iris West -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.

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The Flash -- "Cause and Effect" -- FLA321b_0337b.jpg -- Pictured (L-R): Grant Gustin as Barry Allen and Candice Patton as Iris West -- Photo: Katie Yu/The CW -- © 2017 The CW Network, LLC. All rights reserved.