Holmes and Watson retrace Holmes’ steps after he finds himself in possession of a severed head and no memory of the past six hours or why he has it.

Clive, Ravi, Peyton and Major work together to help Liv.

In the wake of Rip's shooting, Graves and the SEALs plan their payback; Michael lands in CIA custody at a black site; CIA agent Gina Cline pools her resources to find the mastermind behind the attack.

Supergirl is stunned to discover that a part of Krypton survived. Meanwhile, Alex is attacked while out with Ruby, and Lena considers how far she will go to keep Reign contained.