While the team investigates a biker killed in a hit and run, Gibbs prepares to testify against a financial advisor who stole millions from his Navy clients.

Young Kara experiences kryptonite for the first time, Nia and Brainy are trapped by aliens, and a young Cat Grant may be the reason Supergirl never gets out of the Phantom Zone.

With Frost facing an unjust punishment for her past crimes, Caitlin goes to great lengths to save her sister. Meanwhile, Barry's efforts to protect Speed Force Nora lead to a shocking discovery.

Jimmy surprises a Supermom for Mother’s Day before playing the One-Second Viral Video Quiz with Andrew Garfield, chatting with Sara Bareilles, Renée Elise Goldsberry, Paula Pell and Busy Philipps of Girls5eva and welcoming musical guest Thomas Rhett.