Supergirl is called into action when remnants of Cadmus attempt to assassinate pro-alien leaders, but their endgame turns out to be more sinister than she thinks.
Did You Know?
In one of Chyler Leigh's earlier roles on "7th Heaven" (1996), she played Frankie, the teen mother of a baby girl named Mercy. In this season of "Supergirl", Chyler once again is on a show with a character named Mercy -- only this time it's not her daughter but a villain. See more
The cops at the Madrid museum wear the uniform of Pamplona's local police. See more
I used the info you got from Lillian Luthor and found a location for Mercy and Otis. Would you believe it's an abandoned warehouse?