非常警觉 meaning in English

have eyes in the back of his head

The old people had been guarded and suspicious in their own house .
上了年纪的人都非常警觉，就连在自己家里也十分小心多疑。
Only a very alert person can be aware for even that long
只有一个非常警觉的人能够做到。
He withdrew his attention to his paper very circumspectly , listening mentally for the little sounds which should show him what was on foot
他非常警觉地把注意力又转向报纸，心里却在留神她的动静，想弄明白究竟出了什么事。
But he gave no sign . he became immensely wary , for he was wise with knowledge of the low cunning and foul vileness of his kind
血淋漓地流了下来，但他没动声色只是非常警觉了，因为他头脑聪明，深知自己这类人的狡猾与肮脏卑鄙。