He was to be the unseen listener, the keen investigator who had advanced along the trail.

The speakers were scarcely a dozen feet away from this unseen listener.

He was an unseen listener to this conference of criminals.

Already, the unseen listener was completing plans for an immediate campaign.

Blade sensed that now the unseen listeners and watchers were gone.

Even now she whispered, hoping to evade the unseen listeners.

An unseen listener couldn't have wanted a better signal.

Not for an instant did it occur to him that another unseen listener might be here!

Beyond the window had been a form in black - the figure of an unseen listener who had scaled the wall to hear.

Though he didn't know it, Mogridge was explaining everything for the benefit of two unseen listeners.