The DEO bring William in to try to get through to Rip Roar.

Someone with powers infiltrates the DEO, and tries to get to Rip Roar before Supergirl stops her. She gets away. It is Andrea.

Andrea goes to Lena for her help to break into the DEO. She tells her that she is working for the people behind the tidal wave, and they want her to kill Rip Roar. 

However, she does not want to kill him.

In a flashback, Andrea befriends Lena at Mount Helena Boarding School. Lena tells her about how her mom was obsessed with finding the Medallion of Acrata.

Five years later, Lex fires Lena from Lex Corp. Obsidian Worldwide is about to lose billions of dollars from a failed phone launch.

Lena wants Andrea to help her find the Medallion because it will help her stop Lex's obsession with killing Superman.

Lena and Andrea go to Costa Rica. Andrea falls into a hole where she finds the Medallion.

A man appears, he tells her Leviathan sent him. He tells her that in order to save her father, who is on the brink of suicide, she must take the Medallion for herself and pledge her allegiance to Leviathan.

Obsidian's stock flourishes. Lex is arrested when he turns the sun red.

Lena follows Jack to London. She sees Andrea there wearing the Medallion. She cuts ties with her.

Lena leaves Metropolis and Jack. She's goes to National City because of Supergirl and aspires to help people just like she does.

Andrea meets Russell. They start dating.

Kara intercepts incriminating Lex Corp emails and gives them back to Lena. Lena tells her she's not interested in her friendship.

The old lady from Leviathan finds Andrea and tells her to kill a man. Andrea refuses at first, but the lady threatens her father.

The Medallion gives her powers and she kills the man.

Kara gets through to Lena and they have dinner.

Russell gets too close to finding out Andrea's secret. Leviathan is about to kill him when Andrea tells them he can be useful.

Leviathan turns him into Rip Roar.

Lena sells CatCo to Andrea. 

In the present day, Andrea shows Lena the powers the Medallion gives her. They make amends and Lena agrees to help her.

Rip Roar tells Supergirl that Leviathan is behind the attacks.

Lena stages a distress call and Kara goes to her. Andrea plants Lena's new inception device at the DEO. Everyone falls under the influence of it besides Alex.

Andrea escapes with Rip Roar.

Lena threatens to incept Russell to kill himself unless Andrea gives her the Medallion. She does, and her and Russell leave.

Leviathan kills Russell. They tell Andrea that the Medallion brought out the dark powers from within her.

Lena translates the markings on the Medallion; they read "Leviathan."