Sentence:  Captain Edward Carlisle, soldier as he was, martinet as he was, felt a curious sensation of helplessness <WSD>seize upon</WSD> him as he met her steady gaze, her alluring smile; he could not tell what this prisoner might do. 
Meaning of the word marked with <WSD> tags:  To take up, embrace, enact, or turn eagerly to (a plan, idea, ideology, cause, practice, method, etc.); to grasp, understand, and accept quickly; to adopt wholeheartedly or vigorously.