Frank defends Elizabeth when Joshua orders her to get info on Caleb from Ali. Joshua thinks Frank could be an asset to him. Lucy and Ian go to Rafe's and realize the music notes Kevin deciphered match the missing piece to the map and lead to Caleb's building. Caleb convinces Tess she can't return to her cave life and, realizing he loves her, she agrees to go home with him. Elizabeth ask what Rafe & Ali know about Caleb. Ian & Lucy run into Kevin at Caleb's and they find a secret under-ground door. Ian picks the lock and they hide inside as Tess & Caleb arrive. Caleb locks the door, trapping them together.