The Queen Strikes Back (迷宮にひそむ契約 Meikyū ni Hisomu Keiyaku) is the eleventh episode of Phi Brain: Kami no Puzzle Season One and the eleventh episode of the anime series overall.
Elena enlists the help of Kaito and his friends as extras in a new sentai show she is starring in. Later that night, Elena brings everyone together for a Kenja Puzzle in which they must construct a three-dimensional puzzle within a time limit or else be electrocuted. As Elena makes the puzzle harder by throwing in a remote controlled UFO in the works, the POG president Herbert Muller sends in more explosive variants against Elena's wish. After everyone works together to stop the bombs and protect Elena, Kaito enters his Orpheus state and solves the puzzle in the last minute, revealing the treasure to be a puzzle book Elena had when she was younger. Meanwhile, the HQ President is relieved of his duty for his unfair ways.