恰恰在这时，正好在此时
If something happens on cue, it happens just after someone has said or thought it would happen.
I was just wondering where Sarah was, when, right on cue, she came in. 我正纳闷萨拉去哪了，恰在这时，她就进来了。
I was talking to Betty about our first aid course when, as if on cue, a man in front of us fainted.
She mentioned her many admirers and right on cue, a handsome young man appeared at the door.
I had just sat down for lunch when, right on cue, the fire alarm went off.
"It's too dangerous" she insisted, and almost on cue, the sound of an explosion could be heard.
See also: cue noun (SIGNAL)