心の片隅{かたすみ}に、心の奥でNeil always had revenge at the back of his mind. ニールはいつも心の奥に恨みを持っていた。back of one's mind: 内心{ないしん}、心中{しんちゅう}bring one's mind back to: ~を思い出させるcast back in one's mind to: 過去を振り返る、過去に心を向ける